A hall type vehicle speed sensor signal processing circuit

Abstract

The application discloses a Hall type vehicle speed sensor signal processing circuit, which realizes fault diagnosis of short circuit of a vehicle speed sensor signal to ground, short circuit of the vehicle speed sensor signal to a power supply and open circuit, and also realizes discrimination and distinction of 0 rotation speed of the vehicle speed sensor and short circuit to ground and short circuit to the power supply, and meets HSR requirements of engine controller function safety. The Hall type vehicle speed sensor signal processing circuit comprises a double level conversion circuit, a filter protection circuit and a digital-to-analog conversion circuit, wherein the double level conversion circuit is powered by a power supply of the vehicle speed sensor, and an input end of the double level conversion circuit is connected with a same phase signal of the vehicle speed sensor; an input end of the filter protection circuit is connected with an output end of the double level conversion circuit, and an output end of the filter protection circuit is connected with an I / O port of a single-chip microcomputer; an input end of the digital-to-analog conversion circuit is connected with the output end of the double level conversion circuit, and an output end of the digital-to-analog conversion circuit is connected with an AD port of the single-chip microcomputer.

Description

Technical Field

[0001] This application relates to the field of signal processing circuit technology, and more specifically, to a Hall-type vehicle speed sensor signal processing circuit. Background Technology

[0002] As the information source of the automotive electronic control system, the vehicle speed sensor is a key component of the automotive electronic control system. It is a device used to detect the speed of the electronically controlled vehicle and has other functions such as controlling the engine idle speed, torque converter lock-up of the automatic transmission, automatic transmission shifting, engine cooling fan opening and closing, and cruise control based on the input signals sent by the sensor.

[0003] Currently, the output signal of the vehicle speed sensor on a diesel engine is basically a Hall effect digital signal. The vehicle speed sensor is usually installed in the drive axle housing or transmission housing. The vehicle speed sensor signal wire is usually installed in a shielded jacket. This setting is to eliminate electromagnetic and radio frequency interference generated by high-voltage wires and car telephones or other electronic devices, so as to ensure that electronic communication is not interrupted and to prevent deterioration of driving performance or other problems. Magnetoelectric and photoelectric sensors are the two most widely used vehicle speed sensors in automobiles. Magnetoelectric sensors are widely used in various automobiles in Europe, North America and Asia to control vehicle speed (VSS), crankshaft angle (CKP) and camshaft angle (CMP). They can also be used to sense the speed and position indicators of other rotating parts, such as the compressor clutch.

[0004] Currently, with the advancement of engine control technology, especially the promotion and application of the ISO 26262 "Functional Safety of Road Vehicles" international standard in recent years, advanced engine systems must meet the requirements of ISO 26262. The engine controller, as the core of the engine system, must be designed based on functional safety standards developed according to the characteristics of safety-related electronic and electrical systems. According to the functional safety (HSR) requirements for engine controllers, the vehicle speed sensor signal processing circuit of the controller, which measures vehicle speed, must be able to diagnose faults such as short circuit to ground, short circuit to power supply, and open circuit. It must also be able to distinguish between zero speed and short circuits to ground or power supply. However, in existing technologies, the vehicle speed sensor signal is simply processed and directly output to a microcontroller. The circuit is very simple and can only diagnose whether there is a short circuit or open circuit fault at the vehicle speed sensor signal interface. It cannot distinguish between short circuits and open circuit faults. Therefore, the existing technical solution cannot meet the functional safety requirements, posing significant safety hazards to the engine system and the vehicle, and easily causing substantial personal injury and property damage. Summary of the Invention

[0005] This application provides a Hall-type vehicle speed sensor signal processing circuit, which can realize fault diagnosis of vehicle speed sensor signal short circuit to ground, short circuit to power supply, and open circuit, and simultaneously realize the distinction between zero speed of vehicle speed sensor and short circuit to ground or short circuit to power supply, thus meeting the functional safety HSR requirements of engine controller.

[0006] The specific technical solution is as follows:

[0007] This application provides a Hall effect vehicle speed sensor signal processing circuit, including:

[0008] A dual-level conversion circuit is provided, which is powered by the power supply of the vehicle speed sensor, and the input terminal of the dual-level conversion circuit is connected to the in-phase signal of the vehicle speed sensor.

[0009] A filtering protection circuit is provided, wherein the input terminal of the filtering protection circuit is connected to the output terminal of the dual-level conversion circuit, and the output terminal of the filtering protection circuit is connected to the I / O port of the microcontroller.

[0010] A digital-to-analog converter circuit is provided, wherein the input terminal of the digital-to-analog converter circuit is connected to the output terminal of the dual-level conversion circuit, and the output terminal of the digital-to-analog converter circuit is connected to the AD port of the microcontroller.

[0011] Optionally, the dual-level conversion circuit includes resistors R7, R8, and R9. One end of resistor R7 is connected to the power supply, and the other end of resistor R7 is connected to the filter protection circuit, one end of resistor R8, and the I_F_VSS signal of the vehicle speed sensor. The other end of resistor R8 is connected to one end of resistor R9 and the digital-to-analog conversion circuit, and the other end of resistor R9 is grounded.

[0012] Optionally, the filter protection circuit includes a resistor R10, a capacitor C2, and a Zener diode D1. One end of the resistor R10 is connected to the other end of the resistor R7. The other end of the resistor R10 is connected to one end of the capacitor C2 and the I / O port of the microcontroller. One end of the Zener diode D1 is connected to the other end of the resistor R10 and the I / O port of the microcontroller. The other ends of the capacitor C2 and the Zener diode D1 are grounded.

[0013] Alternatively, the Zener diode D1 may be of model BZX84B5V1LT.

[0014] Further optionally, the digital-to-analog conversion circuit includes resistors R1 and R2, capacitors C3 and C1, one end of resistor R1 is connected to the other end of resistor R8, the other end of resistor R1 is connected to one end of capacitor C3 and one end of resistor R2 respectively, the other end of resistor R2 is connected to one end of capacitor C1 and the AD port of the microcontroller respectively, and the other ends of capacitor C3 and capacitor C1 are grounded.

[0015] Further optionally, the dual-level conversion circuit is connected to the internal processing circuit of the vehicle speed sensor via a non-inverting output circuit, and the internal processing circuit is also connected to an inverting output circuit.

[0016] Optionally, the non-inverting output circuit includes resistors R3 and R4 and transistor Q1. The base of transistor Q1 is connected to the internal processing circuit, the emitter of transistor Q1 is grounded, the collector of transistor Q1 is connected to one end of resistor R3 and one end of resistor R4, the other end of resistor R3 is connected to the power supply, the other end of resistor R4 is the OUT1 port, and the other end of resistor R4 is connected to the other end of resistor R7 and one end of resistor R8.

[0017] Alternatively, the transistor Q1 may be an NPN transistor.

[0018] Alternatively, the inverting output circuit includes resistors R5 and R6 and transistor Q2. The base of transistor Q2 is connected to the internal processing circuit, the emitter of transistor Q2 is grounded, the collector of transistor Q2 is connected to one end of resistor R5 and one end of resistor R6, the other end of resistor R5 is connected to the power supply, and the other end of resistor R6 is the OUT2 port.

[0019] Alternatively, the transistor Q2 may be an NPN transistor.

[0020] The beneficial effects of the embodiments of this application are as follows:

[0021] This application solves the safety problems existing in the prior art, and can meet the functional safety (HSR) requirements of engine controllers. It can diagnose faults such as short circuit to ground, short circuit to power supply, and open circuit of Hall-type vehicle speed sensor signals. It can also distinguish between zero speed and short circuit to ground or short circuit to power supply of Hall-type vehicle speed sensors. In addition, the signal processing circuit of this Hall-type vehicle speed sensor has an ingenious principle, uses few components and has extremely low cost. Without affecting the normal vehicle speed signal acquisition, it meets all the fault diagnosis requirements of ISO26262 functional safety, and has strong practicality. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A block diagram of the signal processing circuit for a Hall-type vehicle speed sensor provided in an embodiment of this application;

[0024] Figure 2 The schematic diagram shows the signal processing circuit of the Hall-type vehicle speed sensor provided in the embodiment of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0027] In existing technology, the signal processing circuit of the Hall-type vehicle speed sensor in the engine controller is very simple, typically consisting of a pull-down resistor and a filter circuit. The pull-down resistor provides the initial state (low level) of the vehicle speed signal, the filter circuit filters the signal, and the microcontroller acquires and processes the vehicle speed signal. The Hall-type vehicle speed sensor obtains high and low level signals by sensing the engine speed gear. After processing by the sensor's built-in processing circuit, a PWM signal is output to the engine controller. The engine controller's vehicle speed processing circuit then performs simple processing, and the microcontroller completes the acquisition and processing of the vehicle speed signal. In other words, the simply processed vehicle speed signal is directly output to the microcontroller, which then performs the acquisition and analysis of the vehicle speed signal. The vehicle speed signal is actually a PWM signal; the microcontroller measures the vehicle speed by acquiring the PWM signal frequency. This configuration of the vehicle speed sensor signal processing circuit fails to meet the ISO26262 functional safety HSR requirements. It cannot diagnose or differentiate between short circuits to ground, short circuits to power, and open circuits in the vehicle speed sensor signal. Furthermore, it cannot distinguish between a vehicle speed sensor signal of 0 RPM and a short circuit to ground or power. In other words, the engine controller cannot identify whether the vehicle speed sensor signal is 0 RPM or a short circuit to ground or power. It should be noted that the aforementioned 0 RPM signal could be either high or low.

[0028] To address the problems in the prior art described above, this application discloses a Hall-type vehicle speed sensor signal processing circuit. These will be described in detail below.

[0029] The Hall-type vehicle speed signal is actually a PWM signal (50% duty cycle). In some embodiments, the high level VH of the Hall-type vehicle speed sensor is 10.5V and the low level VL is 0.8V. The microcontroller measures the vehicle speed by acquiring the frequency of the PWM signal.

[0030] Figure 1 A Hall-effect vehicle speed sensor signal processing circuit according to an embodiment of this application is shown. For example... Figure 1 As shown, the signal processing circuit of this Hall-type vehicle speed sensor mainly includes: a dual-level conversion circuit 1, a filter protection circuit 2, and a digital-to-analog conversion circuit 3. Specifically, the dual-level conversion circuit 1 is powered by the power supply 5 of the vehicle speed sensor 6, and the input terminal of the dual-level conversion circuit 1 is connected to the in-phase signal of the vehicle speed sensor 6; the input terminal of the filter protection circuit 2 is connected to the output terminal of the dual-level conversion circuit 1, and the output terminal of the filter protection circuit 2 is connected to the I / O port of the microcontroller 4; the input terminal of the digital-to-analog conversion circuit 3 is connected to the output terminal of the dual-level conversion circuit 1, and the output terminal of the digital-to-analog conversion circuit 3 is connected to the AD port of the microcontroller 4.

[0031] In the embodiments of this application, such as Figure 1 As shown, the vehicle speed sensor signal is first processed by a dual voltage divider circuit (i.e., dual-level conversion circuit 1). The processed signal is then processed separately through two channels, and the processed signals are output to the microcontroller 4. Finally, the microcontroller 4 performs a simple judgment to diagnose faults such as short circuit to ground, short circuit to power supply, and open circuit of the vehicle speed sensor signal. It also distinguishes between zero speed of the vehicle speed sensor and short circuit to ground or short circuit to power supply, so as to meet the functional safety HSR requirements of the engine controller.

[0032] Among them, such as Figure 1 As shown, the vehicle speed signal from the first channel, after undergoing double voltage division processing, is filtered and protected by the filter protection circuit 2 before being directly output to the I / O port of the microcontroller 4 for vehicle speed signal acquisition and processing, achieving normal vehicle speed signal acquisition. The vehicle speed signal from the second channel, after undergoing double voltage division processing, is converted from a PWM digital signal to an analog signal by the digital-to-analog converter circuit 3, and then acquired through the AD port of the microcontroller 4. After acquiring the signals from the first and second channels respectively, the microcontroller 4 uses a simple software application algorithm to achieve normal signal acquisition, distinguish between normal and fault signals, and perform fault signal diagnosis and fault state differentiation.

[0033] In one embodiment, such as Figure 1 and Figure 2 As shown, the dual-level conversion circuit 1 includes resistors R7, R8, and R9. One end of resistor R7 is connected to the power supply 5, and the other end of resistor R7 is connected to the filter protection circuit 2, one end of resistor R8, and the I_F_VSS signal of the vehicle speed sensor 6. The other end of resistor R8 is connected to one end of resistor R9 and the digital-to-analog converter circuit 3, and the other end of resistor R9 is grounded. The filter protection circuit 2 includes resistor R10, capacitor C2, and Zener diode D1. One end of resistor R10 is connected to the other end of resistor R7, and the other end of resistor R10 is connected to one end of capacitor C2 and the I / O port of the microcontroller 4. One end of Zener diode D1 is connected to the other end of resistor R10 and the I / O port of the microcontroller 4, and the other end of capacitor C2 and the other end of Zener diode D1 are grounded. In the specific implementation, the model of Zener diode D1 is BZX84B5V1LT. The digital-to-analog converter circuit 3 includes resistors R1 and R2, capacitors C3 and C1. One end of resistor R1 is connected to the other end of resistor R8. The other end of resistor R1 is connected to one end of capacitor C3 and one end of resistor R2. The other end of resistor R2 is connected to one end of capacitor C1 and the AD port of microcontroller 4. The other ends of capacitor C3 and capacitor C1 are grounded.

[0034] In another embodiment, such as Figure 1 and Figure 2As shown, the dual-level conversion circuit 1 is connected to the internal processing circuit of the vehicle speed sensor 6 via a non-inverting output circuit, and the internal processing circuit is also connected to an inverting output circuit. Specifically, the non-inverting output circuit includes resistors R3 and R4, and transistor Q1. The base of transistor Q1 is connected to the internal processing circuit, the emitter of transistor Q1 is grounded, and the collector of transistor Q1 is connected to one end of resistor R3 and one end of resistor R4. The other end of resistor R3 is connected to the power supply 5, and the other end of resistor R4 is the OUT1 port. The other end of resistor R4 is also connected to the other end of resistor R7 and one end of resistor R8. Further, the inverting output circuit includes resistors R5 and R6, and transistor Q2. The base of transistor Q2 is connected to the internal processing circuit, the emitter of transistor Q2 is grounded, and the collector of transistor Q2 is connected to one end of resistor R5 and one end of resistor R6. The other end of resistor R5 is connected to the power supply 5, and the other end of resistor R6 is the OUT2 port. In some specific implementations, transistor Q1 is an NPN transistor. In other specific implementations, transistor Q2 is an NPN transistor.

[0035] In the embodiments of this application, such as Figure 2 As shown, V12 is a 12V power supply used to power the Hall-type vehicle speed sensor and its signal processing circuit. OUT1 is the in-phase signal output of the vehicle speed sensor, which is connected to the engine controller for processing; OUT2 is the in-phase signal output of the vehicle speed sensor, which is unused and idle. P00.1 is the processed vehicle speed sensor signal, directly connected to the engine controller port. AD01 is the processed vehicle speed sensor signal, converting the PWM digital signal into an analog signal and then directly outputting it to the microcontroller's AD port. I_F_VSS is the vehicle speed signal, output from the vehicle speed sensor to the engine controller's vehicle speed signal processing circuit, in PWM form. Va is the vehicle speed signal processed by a dual voltage divider circuit. When the vehicle speed signal is normally connected to the engine controller, Va and I_F_VSS signal levels differ, but other signal characteristics are completely identical. Vb is the vehicle speed signal processed by the dual voltage divider circuit. Vb and I_F_VSS signal levels differ, but other signal characteristics are completely identical. Vc is the signal level at P00.1, and Vd is the signal level at AD01.

[0036] like Figure 2The internal circuit of the Hall-type vehicle speed sensor shown indicates that it integrates a signal processing circuit and sends the processed vehicle speed signal to the engine controller's vehicle speed signal processing circuit for further processing. Resistors R3 and R4, along with NPN transistor Q1, constitute the non-inverting output circuit of the vehicle speed sensor. When transistor Q1 is off, V12 outputs a high level through resistors R3 and R4, forming a parallel connection between R3, R4, and R7. When transistor Q1 is on, resistor R4 is connected to ground through Q1, forming a parallel connection with the series resistors (R8 and R9). Resistors R5 and R6, along with NPN transistor Q2, constitute the inverting output circuit of the vehicle speed sensor. Its operating principle is the same as the non-inverting output circuit, but because the base control signals of transistors Q1 and Q2 are inverted, the output inverted vehicle speed signal has the opposite level to the non-inverting vehicle speed signal. In some specific implementations, such as... Figure 2 As shown, resistor R3 is 10KΩ, 1% accuracy, 0603 package; resistor R4 is 1.5KΩ, 1% accuracy, 0603 package.

[0037] like Figure 2 The Hall-effect vehicle speed sensor signal processing circuit shown, without considering the internal resistance of the Hall-effect vehicle speed sensor, uses resistors R7, R8, and R9 to form a basic double-level conversion circuit with the internal resistance of the Hall-effect vehicle speed sensor. Specifically, when Va is the signal output port, resistor R7 and the series resistor (i.e., the sum of resistors R8 and R9) form the first voltage divider resistor; when Vb is the signal output port, the series resistor (i.e., the sum of resistors R7 and R8) and resistor R9 form the second voltage divider resistor. Simultaneously, the series resistors R8 and R9 also act as pull-down circuits, ensuring the initial state of the given signal is low to prevent uncertain port states during microcontroller initialization. In some specific implementations, such as... Figure 2 As shown, resistor R7 is 49.9KΩ, 1% precision, 0603 package; resistor R8 is 8.06KΩ, 1% precision, 0603 package; resistor R9 is 2KΩ, 1% precision, 0603 package.

[0038] If we consider the states of the I_F_VSS signal port, such as normal signal access, short circuit to ground, short circuit to power supply, open circuit, and vehicle speed signal of 0, the dual voltage divider circuit will become more complex, and the corresponding signal data will be very different. This is one of the innovations of this application and also the key to achieving the functional safety requirements of ISO26262.

[0039] Resistor R10 and capacitor C2 form a simple low-pass filter circuit. Zener diode D1 is used to ensure that the maximum signal level input to the microcontroller does not exceed the Zener diode's voltage regulation value, thus protecting the microcontroller. P00.1 is directly connected to the microcontroller's pin, and the processed signal is directly output to the microcontroller in the controller, where the microcontroller performs signal processing. When Va is greater than the Zener diode D1's voltage regulation value, the voltage drop across resistor R10 is Va-Vd, and the current flowing through resistor R10 is (Va-Vd) / 10kJ. When Va is not greater than the Zener diode D1's voltage regulation value, the voltage drop across resistor R10 is 0, Va = Vd, the microcontroller's port is in a high-impedance state, and the current flowing through resistor R10 is almost negligible. In some specific implementation processes, such as... Figure 2 As shown, resistor R10 is 10KΩ, 0603 package; capacitor C2 has a capacitance of 220pF / 50V; Zener diode D1 is a 5.1V Zener diode.

[0040] Resistor R1, capacitor C3, resistor R2, and capacitor C1 constitute a digital-to-analog converter circuit, which converts digital signals into analog signals through a two-stage RC filter. In some specific implementation processes, such as... Figure 2 As shown, resistor R1 is 10KΩ, 0603 package; capacitor C3 has a capacitance of 0.1uF / 50V; resistor R2 is 10KΩ, 0603 package; capacitor C1 has a capacitance of 0.1uF / 50V. The digital-to-analog converter (DAC) circuit's filter cutoff frequency = 1 / 2πRC = 159Hz, which meets the filtering requirements for the typical input signal frequency range of the vehicle speed sensor (1Hz–4kHz), enabling the conversion of the frequency signal into a smooth analog signal. The DAC circuit's filtering time = 2RC = 2ms, meaning the DAC circuit causes a 2ms signal delay. For analog signals, a 2ms signal delay is perfectly acceptable.

[0041] In this application, the dual-level conversion circuit, the digital-to-analog conversion circuit, and the dual-channel signal processing are all innovations of the Ben Hall type vehicle speed sensor signal processing circuit. By cooperating with the dual-level conversion circuit and the digital-to-analog conversion circuit in conjunction with the normal vehicle speed sensor signal processing circuit, without affecting the normal vehicle speed signal acquisition, the single-chip microcomputer software joint diagnostic mechanism can realize the fault diagnosis of vehicle speed sensor signal short circuit to ground, short circuit to power supply, and open circuit. At the same time, it can also realize the discrimination between vehicle speed sensor 0 speed (and even distinguish between high level and low level) and short circuit to ground and short circuit to power supply, thus meeting the functional safety HSR requirements of engine controller ISO26262.

[0042] In summary, this Hall-effect vehicle speed sensor signal processing circuit solves the problem that existing vehicle speed sensor processing circuits cannot meet the functional safety requirements of ISO26262. It also resolves the engine controller's inability to accurately identify vehicle speed sensor signal fault states, including short circuit to ground, short circuit to 12V power supply, short circuit to battery positive terminal, and open circuit. Furthermore, it addresses the engine controller's inability to distinguish whether the vehicle speed sensor signal indicates 0 RPM, a short circuit to ground, or a short circuit to power supply. In addition, through a unique and ingenious circuit design, this Hall-effect vehicle speed sensor signal processing circuit solves various known fault diagnosis challenges that Hall-effect vehicle speed sensor signals may encounter, and enables the diagnosis and identification of these faults.

[0043] The above describes the various components of the Hall-type vehicle speed sensor signal processing circuit provided in the embodiments of this application and their interconnections. The following section, in conjunction with... Figure 1 – Figure 2 This paper describes the signal processing circuit of the Hall-type vehicle speed sensor from multiple aspects, including a detailed description and calculation of relevant parameters for normal signal input, short circuit to ground, short circuit to power supply, open circuit, high level at 0 RPM, and low level at 0 RPM, in order to verify the correctness, reliability and accuracy of the signal processing circuit of the Hall-type vehicle speed sensor of this application.

[0044] When the program of the microcontroller 4 detects an abnormality in the speed signal of the acquired P00.1, it will enter the vehicle speed signal processing circuit diagnostic model and perform joint diagnosis with AD01 to determine the fault status.

[0045] 1. When I_F_VSS receives a normal vehicle speed signal

[0046] The Hall-effect vehicle speed signal is a PWM frequency signal (vehicle speed signal duty cycle is 50%). The frequency-related parameters have been described above and will not be repeated here. The signal processed by the first and second acquisition channels will differ depending on whether the vehicle speed frequency signal is high or low.

[0047] It should be noted that the high level (or low level) of the normal vehicle speed signal is the high level (or low level) of the frequency signal, which changes periodically with the frequency signal; it is not the same as the high level (or low level) when the vehicle speed signal is 0. During the period when the vehicle speed signal is 0, the high level is a fixed high level and the low level is a fixed low level, until the 0 speed state is exited.

[0048] 1) When the vehicle speed signal is high level

[0049] The formula for calculating the parallel resistance Ra of resistors R3, R4, and R7 is:

[0050] Ra=(R3+R4)×R7 / (R3+R4+R7)

[0051] =(10k+1.5k)×49.9k / (10k+1.5k+49.9k)

[0052] =9.346kΩ Formula 1

[0053] The formula for calculating the voltage level at Va is:

[0054] Va=(R8+R9)×V12 / (Ra+R8+R9)

[0055] =(8.06k+2k)×12V / (9.346k+8.06k+2k)

[0056] =6.22V Formula 2

[0057] Due to the effect of Zener diode D1, the voltage level at Vc is 5.1V, and a voltage drop is formed across resistor R10 at this time:

[0058] V1 = Va - Vc = 6.22V - 5.1V = 1.12V (Formula 3)

[0059] The current I1 flowing through resistor R10 is:

[0060] I1=V1 / R10=1.12V / 10k=1.12mA Formula 4

[0061] The power dissipation P1 of resistor R10 is:

[0062] P1=I1×I1×R10=1.12mA×1.12mA×10k=0.125mW Formula 5

[0063] Based on the aforementioned information, resistor R10 is a 0603 standard package with a maximum power rating of 1 / 10W.

[0064] P1 = 0.125mW << 0.1W

[0065] according to Figure 2 As shown, the Zener diode D1 is model BZX84B5V1LT, with a maximum Zener current of 20mA.

[0066] I1 = 1.12mA << 20mA

[0067] Therefore, the selection parameters of resistor R10 and Zener diode D1 fully meet the design requirements.

[0068] The formula for calculating the voltage level at Vb is:

[0069] VHb=R9×V12 / (Ra+R8+R9)=2k×12V / (9.346k+8.06k+2k)=1.236V Formula 6

[0070] 2) When the vehicle speed signal is low level

[0071] The formula for calculating the parallel resistance Rb of resistors R4, R8, and R9 is:

[0072] Rb=R4×(R8+R9) / (R4+R8+R9)

[0073] =1.5k×(8.06k+2k) / (1.5k+8.06k+2k)

[0074] =1.314kΩ Formula 7

[0075] The formula for calculating the voltage level at Va is:

[0076] Va=Rb×V12 / (R7+Rb)=1.314k×12V / (49.9k+1.314k)=0.308V Formula 8

[0077] Since Va << 5.1V, the voltage level at Vc can be obtained:

[0078] Vc = Va = 0.308V

[0079] At this point, there is no voltage drop across resistor R10, and the Zener current can be ignored.

[0080] The formula for calculating the voltage level at Vb is:

[0081] VLb=Va×R9 / (R8+R9)=0.308V×2k / (8.06k+2k)=0.0612V Formula 9

[0082] 3) AD01 level when the vehicle speed signal is normally connected

[0083] The PWM signal duty cycle is 50%, so the analog signal level at AD01 when the normal vehicle speed signal is received is as follows:

[0084] Vd = VHb × 50% + VLb × 50%

[0085] =1.236V×50%+0.0612V×50%=0.6486V Formula 10

[0086] 2. When I_F_VSS is shorted to ground

[0087] When the engine controller vehicle speed signal port I_F_VSS is shorted to ground (no sensor signal is connected), the relevant parameters of the vehicle speed sensor processing circuit need to be recalculated because the processing circuit is not affected by the internal circuit of the sensor.

[0088] When I_F_VSS is shorted to ground, Va = 0V

[0089] Since Va << 5.1V, the voltage level at Vc can be obtained, Vc = Va = 0V.

[0090] Similarly, at this time, Vb = Vd = Va = 0V

[0091] 3. When I_F_VSS is shorted to power supply Vbat

[0092] When the engine controller vehicle speed signal port I_F_VSS is shorted to the power supply Vbat (no sensor signal is connected), the relevant parameters of the vehicle speed sensor processing circuit need to be recalculated because the processing circuit is not affected by the internal circuit of the sensor.

[0093] The allowable range of the power supply voltage Vbat for the engine controller is 9–32V.

[0094] When I_F_VSS is shorted to the power supply Vbat, Va = Vbat

[0095] Since Vbat > 5.1V, due to the effect of Zener diode D1, Vc = 5.1V.

[0096] At this time, the maximum power dissipation P2 of resistor R7 is:

[0097] P2 = |Vbat - V12|² / R7 Formula 11

[0098] When Vbat = 9V, according to formula 11, P2 = |9V - 12V|² / 49.9k = 0.18mW

[0099] When Vbat = 32V, according to Formula 11, P2 = |32V - 12V|² / 49.9kW = 8.02mW

[0100] At this point, the maximum current I2 of resistor R10 can be obtained according to formulas 3 and 4:

[0101] I² = (Va - Vc) / R10 = (Vbat - 5.1V) / R10 (Formula 12)

[0102] When Vbat = 9V, according to formula 12, I2 = (9V - 5.1V) / 10k = 0.39mA

[0103] When Vbat = 32V, according to formula 12, I2 = (32V - 5.1V) / 10k = 2.69mA

[0104] At this time, the maximum power dissipation P3 of resistor R10 is:

[0105] P3=(Va-Vc)2 / R10 Formula 13

[0106] When Vbat = 9V, according to formula 13, P3 = (9V - 5.1V)² / 10k = 1.521mW

[0107] When Vbat = 32V, according to formula 13, P3 = (32V - 5.1V)² / 10k = 0.072W

[0108] At this time, the maximum power dissipation P4 of resistor R8 is:

[0109] P4=[Vbat×R8 / (R8+R9)]2 / R8 Formula 14

[0110] When Vbat = 9V, according to formula 14, we get

[0111] P4=[9V×8.06k / (8.06k+2k)]2 / 8.06k=6.45mW

[0112] When Vbat = 32V, according to formula 14, we get

[0113] P4=[32V×8.06k / (8.06k+2k)]2 / 8.06k=0.081W

[0114] At this time, the maximum power dissipation P5 of resistor R9 is:

[0115] P5=[Vbat×R9 / (R8+R9)]2 / R9 Formula 15

[0116] When Vbat = 9V, according to formula 15, P5 = [9V × 2k / (8.06k + 2k)]² / 2k = 1.6mW

[0117] When Vbat = 32V, according to formula 15, P5 = [32V × 2k / (8.06k + 2k)]² / 2k = 0.02W

[0118] At this time, the voltage level at Vb is:

[0119] Vb=Vbat×R9 / (R8+R9) Formula 16

[0120] When Vbat = 9V, according to formula 16, Vb = 9V × 2k / (8.06k + 2k) = 1.789V

[0121] When Vbat = 32V, according to formula 16, Vb = 32V × 2k / (8.06k + 2k) = 6.36V

[0122] Therefore, the Vd level can be obtained as follows:

[0123] When Vbat = 9V, Vd = Vc = 1.789V

[0124] When Vbat = 32V, Vd = Vc = 6.36V

[0125] It should be noted that the maximum sampling level of the microcontroller is 5V, and the level measured in the full-scale range is 5V. Vc = 6.36V, and 6.36V ≥ 5V.

[0126] Therefore, when Vbat = 32V, the actual voltage level sampled by the microcontroller's port AD01 is 5V.

[0127] 4. When I_F_VSS is open

[0128] When the engine controller vehicle speed signal port I_F_VSS is open (no sensor signal is connected, port is floating), the relevant parameters of the vehicle speed sensor processing circuit need to be recalculated because the processing circuit is not affected by external factors of the engine controller. However, when the port is shorted to 32V, the selection parameters of resistors R7, R8, R9, and Zener diode D1 all meet the design requirements, and V12 << 32V, so there is no need to recalculate the corresponding parameters when the port is open.

[0129] At this time, the voltage level at Va is:

[0130] Va = V12 × (R8 + R9) / (R7 + R8 + R9)

[0131] =12v×(8.06k+2k) / (49.9k+8.06k+2k)

[0132] =2.013V Formula 17 At this time, the voltage level at Vc is: Vc = Va = 2.013V

[0133] At this time, the voltage level at Vb is:

[0134] Vb = V12 × R9 / (R7 + R8 + R9)

[0135] =12v×2k / (49.9k+8.06k+2k)

[0136] =0.4V Formula 18

[0137] 5. When I_F_VSS receives a 0 RPM signal

[0138] When the engine controller's vehicle speed signal port I_F_VSS receives a 0 RPM signal, the signal may be high or low, so the relevant parameters of the vehicle speed sensor processing circuit need to be recalculated.

[0139] It should be noted that the high level (or low level) of the 0 RPM signal is not the same as the high level (or low level) of the normal vehicle speed signal. During the period when the vehicle speed signal is 0, the high level is a fixed high level and the low level is a fixed low level, until the 0 RPM state is exited.

[0140] 1) When the vehicle speed signal is high level

[0141] The formula for calculating the parallel resistance Ra of resistors R3, R4, and R7 is:

[0142] Ra=(R3+R4)×R7 / (R3+R4+R7)

[0143] =(10k+1.5k)×49.9k / (10k+1.5k+49.9k)

[0144] =9.346kΩ Formula 19

[0145] The formula for calculating the voltage level at Va is:

[0146] Va=(R8+R9)×V12 / (Ra+R8+R9)

[0147] =(8.06k+2k)×12V / (9.346k+8.06k+2k)

[0148] =6.22V Formula 20

[0149] Due to the effect of Zener diode D1, the voltage level at Vc is 5.1V. At this time, a voltage drop is formed across resistor R10:

[0150] V1 = Va - Vc = 6.22V - 5.1V = 1.12V (Formula 21)

[0151] The current I1 flowing through resistor R10 is:

[0152] I1=V1 / R10=1.12V / 10k=1.12mA Formula 22

[0153] The power dissipation P1 of resistor R10 is:

[0154] P1=I1×I1×R10=1.12mA×1.12mA×10k=0.125mW Formula 23

[0155] Based on the foregoing information, resistor R10 is a 0603 standard package with a maximum power rating of 1 / 10W.

[0156] P1 = 0.125mW << 0.1W

[0157] according to Figure 2 As shown, the selected Zener diode D1 is model BZX84B5V1LT, with a maximum Zener current of 20mA.

[0158] I1 = 1.12mA << 20mA

[0159] Therefore, the parameters selected for resistor R10 and Zener diode D1 fully meet the design requirements.

[0160] The formula for calculating the voltage level at Vb is:

[0161] Vb=R9×V12 / (Ra+R8+R9)=2k×12V / (9.346k+8.06k+2k)=1.236V Formula 24

[0162] Therefore, we get Vd = Vb = 1.236V

[0163] 2) When the vehicle speed signal is low level

[0164] The formula for calculating the parallel resistance Rb of resistors R4, R8, and R9 is:

[0165] Rb=R4×(R8+R9) / (R4+R8+R9)

[0166] =1.5k×(8.06k+2k) / (1.5k+8.06k+2k)

[0167] =1.314kΩ Formula 25

[0168] The formula for calculating the voltage level at Va is:

[0169] Va=Rb×V12 / (R7+Rb)=1.314k×12V / (49.9k+1.314k)=0.308V Formula 26

[0170] Since Va << 5.1V, the voltage level at Vc can be calculated as: Vc = Va = 0.308V.

[0171] At this point, there is no voltage drop across resistor R10, and the Zener current can be ignored.

[0172] The formula for calculating the voltage level at Vb is:

[0173] Vb=Va×R9 / (R8+R9)=0.308V×2k / (8.06k+2k)=0.0612V Formula 27

[0174] Therefore, we get Vd = Vb = 0.0612V

[0175] 6. Summary and explanation of various states of the Hall-type vehicle speed sensor signal processing circuit

[0176] Based on the above description, the relevant parameters of the vehicle speed signal under several states, including normal signal access, short circuit to ground, short circuit to power supply, open circuit, high level at 0 RPM, and low level at 0 RPM, are described in detail and calculated. The specific parameters can be summarized in a table, as shown in Table 1 below.

[0177]

[0178] Table 1 Interface Status and Calculation Results

[0179] It should be noted and understood that when the microcontroller program detects an abnormality in the speed signal acquired from P00.1, it will enter the vehicle speed signal processing circuit diagnostic mode to perform joint diagnosis with AD01 to determine the fault status.

[0180] As shown in Table 1 above, the parameters corresponding to various states are completely different. The Hall-type vehicle speed sensor signal processing circuit can fully realize the identification and diagnosis of several states, including normal signal access, short circuit to ground, short circuit to power supply, open circuit, high level at 0 speed, and low level at 0 speed.

[0181] In summary, this specification discloses a Hall-effect vehicle speed sensor signal processing circuit that solves the safety problems existing in the prior art, meets the functional safety (HSR) requirements of engine controllers, and can diagnose faults such as short circuit to ground, short circuit to power supply, and open circuit of the Hall-effect vehicle speed sensor signal. It can also distinguish between zero speed and short circuit to ground or short circuit to power supply. Furthermore, this Hall-effect vehicle speed sensor signal processing circuit has an ingenious principle, uses few components, and is extremely low in cost. Without affecting normal vehicle speed signal acquisition, it meets all the fault diagnosis requirements of ISO26262 functional safety, making it highly practical.

[0182] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application.

[0183] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the above embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A signal processing circuit for a Hall type vehicle speed sensor, characterized by comprising: include: A dual-level conversion circuit is provided, which is powered by the power supply of the vehicle speed sensor, and the input terminal of the dual-level conversion circuit is connected to the in-phase signal of the vehicle speed sensor. A filtering protection circuit is provided, wherein the input terminal of the filtering protection circuit is connected to the output terminal of the dual-level conversion circuit, and the output terminal of the filtering protection circuit is connected to the I / O port of the microcontroller. A digital-to-analog converter circuit, wherein the input terminal of the digital-to-analog converter circuit is connected to the output terminal of the dual-level conversion circuit, and the output terminal of the digital-to-analog converter circuit is connected to the AD port of the microcontroller; The dual-level conversion circuit includes resistors R7, R8, and R9. One end of resistor R7 is connected to the power supply, and the other end of resistor R7 is connected to the filter protection circuit, one end of resistor R8, and the I_F_VSS signal of the vehicle speed sensor. The other end of resistor R8 is connected to one end of resistor R9 and the digital-to-analog conversion circuit, and the other end of resistor R9 is grounded. The filtering and protection circuit includes a resistor R10, a capacitor C2, and a Zener diode D1. One end of the resistor R10 is connected to the other end of the resistor R7. The other end of the resistor R10 is connected to one end of the capacitor C2 and the I / O port of the microcontroller. One end of the Zener diode D1 is connected to the other end of the resistor R10 and the I / O port of the microcontroller. The other ends of the capacitor C2 and the other ends of the Zener diode D1 are grounded. The digital-to-analog converter circuit includes resistors R1 and R2, capacitors C3 and C1. One end of resistor R1 is connected to the other end of resistor R8. The other end of resistor R1 is connected to one end of capacitor C3 and one end of resistor R2. The other end of resistor R2 is connected to one end of capacitor C1 and the AD port of the microcontroller. The other ends of capacitor C3 and capacitor C1 are grounded. The dual-level conversion circuit is connected to the internal processing circuit of the vehicle speed sensor via a non-inverting output circuit, and the internal processing circuit is also connected to an inverting output circuit. The non-inverting output circuit includes resistors R3 and R4, and a transistor Q1. The base of transistor Q1 is connected to the internal processing circuit, the emitter of transistor Q1 is grounded, the collector of transistor Q1 is connected to one end of resistor R3 and one end of resistor R4, the other end of resistor R3 is connected to the power supply, the other end of resistor R4 is the OUT1 port, and the other end of resistor R4 is connected to the other end of resistor R7 and one end of resistor R8. The vehicle speed signal from the first channel, after being processed by the dual-level conversion circuit, is filtered by the filtering and protection circuit and protected by the microcontroller port before being directly output to the microcontroller's I / O port for vehicle speed signal acquisition and processing, achieving normal vehicle speed signal acquisition. The vehicle speed signal from the second channel, after being processed by the dual-level conversion circuit, is converted from a PWM digital signal to an analog signal by the digital-to-analog converter circuit, and then acquired by the microcontroller's AD port. After acquiring the signals from the first and second channels respectively, the microcontroller uses a simple software application algorithm to achieve normal signal acquisition, distinguish between normal and fault signals, and perform fault signal diagnosis and fault state differentiation. The fault states include short circuit to ground, short circuit to power supply, open circuit, high level at 0 RPM, and low level at 0 RPM. When the analog signal level at the AD port of the microcontroller is the duty cycle weighted average of the high and low levels of the signal at the I / O port of the microcontroller, the vehicle speed sensor signal is determined to be a normal signal; otherwise, it is a fault signal. When the analog signal level at the AD port and the signal level at the I / O port of the microcontroller are both 0V, the fault state of the vehicle speed sensor signal is determined to be a short circuit to ground. When the analog signal level at the AD port of the microcontroller is equal to the voltage across resistor R9 in the series voltage divider circuit of resistors R8 and R9, and the signal level at the I / O port of the microcontroller is equal to the voltage regulation value of the Zener diode D1, the fault state of the vehicle speed sensor signal is determined to be a short circuit to the power supply; wherein, the maximum value of the analog signal level at the AD port of the microcontroller is the maximum sampling level of the microcontroller; When the analog signal level at the AD port of the microcontroller is the voltage division value across resistor R9 in the series voltage divider circuit of resistor R8, resistor R9 and equivalent resistor Ra, and the signal level at the I / O port of the microcontroller is the voltage regulation value of the Zener diode D1, the fault state of the vehicle speed sensor signal is determined to be 0 RPM high level; wherein, the equivalent resistor Ra is the parallel equivalent resistance of the series branch of resistor R7, resistor R3 and resistor R4; When the analog signal level at the AD port of the microcontroller is the voltage across resistor R9 after the first stage voltage divider of resistor R7 and equivalent resistor Rb, and the second stage voltage divider of resistor R8 and resistor R9, and the signal level at the I / O port of the microcontroller is the voltage across equivalent resistor Rb in the series voltage divider circuit of resistor R7 and equivalent resistor Rb, the fault state of the vehicle speed sensor signal is determined to be 0 RPM low level; wherein, the equivalent resistor Rb is the parallel equivalent resistance of the series branch of resistor R4, resistor R8, and resistor R9; When the analog signal level at the AD port of the microcontroller is equal to the voltage across resistor R9 in the series voltage divider circuit of resistors R7, R8, and R9, and the signal level at the I / O port of the microcontroller is equal to the total voltage across resistors R8 and R9 in the series voltage divider circuit of resistors R7, R8, and R9, the fault state of the vehicle speed sensor signal is determined to be open circuit.

2. The Hall type vehicle speed sensor signal processing circuit according to claim 1, characterized by, The Zener diode D1 is model BZX84B5V1LT.

3. The Hall-type vehicle speed sensor signal processing circuit according to claim 1, characterized by, The transistor Q1 is an NPN transistor.

4. The Hall-type vehicle speed sensor signal processing circuit according to claim 1, characterized by, The inverting output circuit includes resistors R5 and R6 and transistor Q2. The base of transistor Q2 is connected to the internal processing circuit, the emitter of transistor Q2 is grounded, the collector of transistor Q2 is connected to one end of resistor R5 and one end of resistor R6, the other end of resistor R5 is connected to the power supply, and the other end of resistor R6 is the OUT2 port.

5. The Hall-type vehicle speed sensor signal processing circuit according to claim 4, characterized by The transistor Q2 is an NPN transistor.

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