Interface circuit suitable for wheel speed sensor and data recovery method

Abstract

The invention relates to an interface circuit suitable for a wheel speed sensor and a data recovery method, and the interface circuit comprises a current and voltage conversion unit, a data processing unit which is adaptively connected with the current and voltage conversion unit and is used for generating a wheel speed digital signal corresponding to a wheel speed voltage, and when the wheel speed digital signal is generated, the data processing unit is connected with the current and voltage conversion unit. Comparing the wheel speed voltage with the data recovery threshold voltage to generate a wheel speed digital signal based on a comparison state of the wheel speed voltage and the data recovery threshold voltage; when the wheel speed voltage is switched between the first voltage state and the second voltage state, corresponding data recovery threshold voltage is generated based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal; the generated data restores that the threshold voltage matches the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal. According to the invention, current tracking can be effectively realized, and the precision and reliability of wheel speed recovery are improved.

Description

Technical Field

[0001] The invention relates to an interface circuit and a data recovery method, in particular to an interface circuit and a data recovery method suitable for a wheel speed sensor. Background Art

[0002] Wheel speed sensor is an important sensor in automobiles, which can be used to obtain wheel speed information. Wheel speed sensor is usually installed on the wheel or wheel hub, and can convert the mechanical movement of the wheel into electrical signals for processing by the vehicle's electronic control unit (ECU). Active wheel speed sensor, also known as active wheel speed sensor, is a common wheel speed sensor in automobiles. This sensor needs external power supply to work properly. They are usually designed based on the Hall effect principle, with high frequency response and strong anti-interference ability.

[0003] At present, there are three types of active wheel speed sensors on the market: Type I wheel speed sensor, Type II wheel speed sensor, and Type III wheel speed sensor. These wheel speed sensors can provide vehicle wheel speed as well as information such as wheel steering, forward and reverse rotation, and air gap changes, which can improve the performance of the vehicle control system and the safety of the vehicle.

[0004] The wheel speed sensor interface circuit is used to process the signal from the wheel speed sensor and convert it into a voltage signal that can be recognized by the microcontroller unit (MCU) or electronic control unit (ECU). In addition, the wheel speed sensor interface circuit also provides power for the active wheel speed sensor.

[0005] Generally, wheel speed sensors transmit data via current. Type I wheel speed sensors and Type II wheel speed sensors have two types of current data: low current (7mA) and high current (14mA). Type III wheel speed sensors have three types of current data: low current (7mA), medium current (14mA) and high current (28mA).

[0006] Since the wheel speed sensor interface may have leakage current, the low current of the wheel speed sensor is not exactly 7mA, but a range centered around 7mA. In order to improve the accuracy of the current loaded into the electronic control unit, the interface circuit of the wheel speed sensor needs to have a leakage current compensation circuit to track the leakage current.

[0007] At present, when tracking leakage current, the common method is to track the low current value, then convert the tracked low current into voltage and store it on the capacitor, and then add the threshold to restore the data. However, due to the certain leakage of capacitors in the CMOS process, if the high current lasts for too long, the low current value will not be updated, resulting in data recovery errors, that is, the interface of the existing wheel speed sensor cannot effectively realize leakage current tracking. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide an interface circuit and a data recovery method suitable for a wheel speed sensor, which can effectively realize current tracking and improve the accuracy and reliability of wheel speed recovery.

[0009] According to the technical solution provided by the present invention, an interface circuit suitable for a wheel speed sensor comprises:

[0010] A current-voltage conversion unit is adapted to be connected with the wheel speed sensor, provides working power to the wheel speed sensor, and converts the wheel speed current output by the wheel speed sensor into a corresponding wheel speed voltage;

[0011] A data processing unit is adaptively connected to the current-voltage conversion unit and is used to generate a wheel speed digital signal corresponding to the wheel speed voltage, wherein:

[0012] When generating the wheel speed digital signal, the wheel speed voltage is compared with the data recovery threshold voltage to generate the wheel speed digital signal based on the comparison state of the wheel speed voltage and the data recovery threshold voltage;

[0013] The data recovery threshold voltage is generated based on at least the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, wherein:

[0014] The voltage state of the wheel speed voltage includes at least a first voltage state and a second voltage state;

[0015] When the wheel speed voltage switches between the first voltage state and the second voltage state, a corresponding data recovery threshold voltage is generated based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, so that the generated data recovery threshold voltage matches the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal.

[0016] The data processing unit includes a threshold voltage generating unit and a signal comparing unit, wherein:

[0017] The signal comparison unit is used to compare the wheel speed voltage and the data recovery threshold voltage, and generate a corresponding wheel speed digital signal;

[0018] Based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, the threshold voltage generating unit generates a corresponding data restoration threshold voltage.

[0019] The threshold voltage generating unit includes a first voltage sampling unit, a second voltage sampling unit and a comparison threshold generating circuit, wherein:

[0020] The first voltage sampling unit and the second voltage sampling unit are connected to a comparison threshold generating circuit, and the comparison threshold generating circuit is connected to a first comparison terminal of the signal comparison unit;

[0021] The first voltage sampling unit and the second voltage sampling unit simultaneously receive the wheel speed voltage;

[0022] When the wheel speed voltage is in a first voltage state and the level state of the wheel speed digital signal is a first level state, a first voltage sampling unit is configured to sample and hold the wheel speed voltage, and a first sampled and held voltage generated by the sampled and held voltage is loaded into a comparison threshold generation circuit, and the comparison threshold generation circuit generates a data recovery threshold voltage of a first state based on the first sampled and held voltage;

[0023] When the wheel speed voltage is in the second voltage state and the level state of the wheel speed digital signal is the second level state, a second voltage sampling unit is configured to sample and hold the wheel speed voltage, and a second sample-and-hold voltage generated by the sample-and-hold is loaded into a comparison threshold generation circuit, and the comparison threshold generation circuit generates a data recovery threshold voltage of the second state based on the second sample-and-hold voltage.

[0024] When the wheel speed voltage in the first voltage state is lower than the wheel speed voltage in the second voltage state, the first level state of the wheel speed digital signal is a low level, the second level state of the wheel speed digital signal is a high level, and the data recovery threshold voltage in the second state is greater than the data recovery threshold voltage in the first state.

[0025] The first voltage sampling unit includes a voltage sampling first unit gain follower buffer, a voltage sampling first switch, a voltage sampling first resistor and a voltage sampling first capacitor, wherein:

[0026] The input end of the voltage sampling first unit gain follower buffer receives the wheel speed voltage, the output end of the voltage sampling first unit gain follower buffer is connected to one end of the voltage sampling first switch, the other end of the voltage sampling first switch is connected through one end of the voltage sampling first resistor, the other end of the voltage sampling first resistor is connected to one end of the voltage sampling first capacitor and the first input end of the comparison threshold generating circuit, and the other end of the voltage sampling first capacitor is grounded;

[0027] When the voltage sampling first switch is in a closed state, the first voltage sampling unit samples and holds the wheel speed voltage through the voltage sampling first capacitor.

[0028] The comparison threshold generating circuit includes a threshold voltage generating first subunit and a threshold voltage generating second subunit, wherein:

[0029] The first voltage sampling unit is adaptively connected to the first subunit generating the threshold voltage, and the second voltage sampling unit is adaptively connected to the second subunit generating the threshold voltage;

[0030] The first threshold voltage generating subunit generates a data recovery threshold voltage of a first state based on the first sample and hold voltage, wherein the data recovery threshold voltage of the first state is the sum of the first sample and hold voltage and the threshold adjustment voltage;

[0031] The threshold voltage generating second subunit generates a data recovery threshold voltage of a second state based on the second sample and hold voltage, wherein the data recovery threshold voltage of the second state is a difference between the second sample and hold voltage and the threshold adjustment voltage.

[0032] The threshold voltage generating first subunit includes a voltage generating first voltage follower, a threshold adjusting first voltage unit and a threshold generating first switch, wherein:

[0033] The input end of the voltage generating first voltage follower receives the first sample and hold voltage, and the output end of the voltage generating first voltage follower is connected to the first end of the threshold generating first switch through the threshold adjusting first voltage unit;

[0034] The second end of the threshold generating first switch is connected to the first comparison end of the signal comparison unit;

[0035] When the first voltage sampling unit is configured to sample and hold the wheel speed voltage, the threshold generating first switch is configured to be in a closed state at the same time, so as to load the generated first state data recovery threshold voltage to the first comparison terminal of the signal comparison unit.

[0036] The threshold adjustment voltage is at least half of the sum of the wheel speed voltage value in the first voltage state and the vehicle speed voltage value in the second voltage state.

[0037] The signal comparison unit at least includes a voltage comparator, wherein:

[0038] The inverting terminal of the voltage comparator forms a first comparison terminal of the signal comparison unit, and the non-inverting terminal of the voltage comparator forms a second comparison terminal of the signal comparison unit;

[0039] The wheel speed voltage is loaded to the second comparison terminal of the signal comparison unit.

[0040] A data recovery method suitable for a vehicle speed sensor, for any wheel speed sensor, uses the above-mentioned interface circuit to connect and cooperate with the wheel speed sensor, so as to utilize the interface circuit to process the speed information detected by the wheel speed sensor to generate a corresponding wheel speed digital signal.

[0041] The advantages of the present invention are as follows: when generating a wheel speed digital signal, the wheel speed voltage is compared with the data recovery threshold voltage to generate the wheel speed digital signal based on the comparison state of the wheel speed voltage and the data recovery threshold voltage; when the wheel speed voltage switches between a first voltage state and a second voltage state, a corresponding data recovery threshold voltage is generated based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, so that the generated data recovery threshold voltage matches the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal, thereby improving the accuracy and reliability of wheel speed recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A system block diagram of an embodiment of the interface circuit of the present invention connected with a vehicle-road speed sensor.

[0043] Figure 2 This is a circuit diagram of an embodiment of the first voltage sampling unit of the present invention.

[0044] Figure 3 This is a circuit diagram of an embodiment of the second voltage sampling unit of the present invention.

[0045] Figure 4 The figure is a circuit diagram of an embodiment of a comparison threshold generating circuit of the present invention.

[0046] Figure 5 This is a working timing diagram of an embodiment of the interface circuit of the present invention.

[0047] Explanation of the reference numerals: 1 - current-voltage conversion unit, 2 - first voltage sampling unit, 3 - second voltage sampling unit, 4 - comparison threshold generating circuit. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific drawings and embodiments.

[0049] In order to effectively realize current tracking and improve the accuracy and reliability of wheel speed recovery, the present invention provides an interface circuit suitable for a wheel speed sensor. Specifically, the interface circuit includes:

[0050] The current-voltage conversion unit 1 is adapted to be connected with the wheel speed sensor, provides working power to the wheel speed sensor, and converts the wheel speed current output by the wheel speed sensor into a corresponding wheel speed voltage;

[0051] The data processing unit is adaptively connected to the current-voltage conversion unit 1 and is used to generate a wheel speed digital signal corresponding to the wheel speed voltage, wherein:

[0052] When generating the wheel speed digital signal, the wheel speed voltage is compared with the data recovery threshold voltage to generate the wheel speed digital signal based on the comparison state of the wheel speed voltage and the data recovery threshold voltage;

[0053] The data recovery threshold voltage is generated based on at least the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, wherein:

[0054] The voltage state of the wheel speed voltage includes at least a first voltage state and a second voltage state;

[0055] When the wheel speed voltage switches between the first voltage state and the second voltage state, a corresponding data recovery threshold voltage is generated based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, so that the generated data recovery threshold voltage matches the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal.

[0056] As can be seen from the above description, the wheel speed sensor is generally an active type sensor, and the wheel speed detected by the wheel speed sensor is generally output as a current. Therefore, the recovery of the wheel speed specifically refers to converting the wheel speed current output by the wheel speed sensor into a wheel speed digital signal; improving the recovery accuracy of the wheel speed specifically refers to the high matching of the wheel speed digital signal with the wheel speed current, that is, generating a high-precision wheel speed digital signal. It is understandable that the generated wheel speed digital signal can be loaded into the MCU or ECU for subsequent control of the vehicle speed and the like.

[0057] Figure 1 An embodiment of the interface circuit is shown in FIG. 1 . As can be seen from the figure, the interface circuit should include a current-voltage conversion unit 1. The current-voltage conversion unit 1 can provide a working power supply for the wheel speed sensor and convert the wheel speed current into a corresponding wheel speed voltage. The working power supply provided by the current-voltage conversion unit 1 can meet the normal working requirements of the wheel speed sensor. Figure 1 In the figure, WSS is the wheel speed sensor. In the figure, the current-voltage conversion unit 1 is connected to the power supply VSS, so that the power supply VSS can provide the working power supply of the current-voltage conversion unit 1 and the wheel speed sensor. Specifically, the wheel speed current is the wheel speed output by the wheel speed sensor. Figure 5 An embodiment of the wheel speed current is shown in FIG. Figure 5 The idata in is the wheel speed current.

[0058] In order to convert the wheel speed current into wheel speed voltage, Figure 1 An embodiment of a current-voltage conversion unit 1 is provided in the figure, in which the current-voltage conversion unit includes an operational amplifier U1 and a resistor R1, the in-phase end of the operational amplifier U1 is connected to one end of the resistor R1 and a power supply VSS, the inverting end of the operational amplifier U1 is connected to the other end of the resistor R1 and a wheel speed sensor, and the ground end of the wheel speed sensor is grounded. Of course, the current-voltage conversion unit 1 can also adopt other implementation forms, which can be selected according to actual needs, and will not be listed here one by one.

[0059] In order to generate a wheel speed digital signal, the interface circuit should also include a data processing unit, which should be adaptively connected to the current-voltage conversion unit 1 to load the wheel speed voltage to the data processing unit. Figure 1 and Figure 5 In the figure, Vdata is the wheel speed voltage. When generating the wheel speed digital signal, at least the wheel speed voltage is compared with the data recovery threshold voltage, so that the wheel speed digital signal can be generated according to the comparison state of the wheel speed voltage and the data recovery threshold voltage, wherein the comparison state specifically refers to the size state between the wheel speed voltage and the data recovery threshold voltage, such as the wheel speed voltage is not less than the data recovery threshold voltage, or the wheel speed voltage is less than the data recovery threshold voltage. Specifically, when the wheel speed voltage is less than the data recovery threshold voltage, a low level of the wheel speed digital signal can be generated, and when the wheel speed voltage is not less than the data recovery threshold voltage, a high level of the wheel speed digital signal can be generated.

[0060] It can be seen from the above description that the wheel speed sensor includes Type I wheel speed sensor, Type II wheel speed sensor, and Type III wheel speed sensor. In one embodiment of the present invention, the wheel speed sensor specifically refers to Type I wheel speed sensor or Type II wheel speed sensor. At this time, the wheel speed current can be 7mA or 14mA. Therefore, the converted wheel speed voltage includes a first voltage state and a second voltage state, wherein the wheel speed voltage of the first voltage state can be generated based on the conversion of the wheel speed current of 7mA, and the wheel speed voltage of the second voltage state can be generated based on the conversion of the wheel speed current of 14mA. The first voltage state and the second voltage state of the wheel speed voltage can be selected according to actual needs.

[0061] The level state of the wheel speed digital signal specifically refers to whether the level state of the vehicle speed digital signal is low or high, wherein the low level of the wheel speed digital signal may correspond to one of the wheel speed currents of 7mA or 14mA, and the high level of the wheel speed digital signal may correspond to the wheel speed current of the other magnitude. Figure 5 It can be seen that the wheel speed current output by the wheel speed sensor will switch between 7mA and 14mA, so the wheel speed voltage will switch between the first voltage state and the second voltage state. In order to improve the accuracy and reliability of wheel speed recovery, the present invention generates a corresponding data recovery threshold voltage based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal. At this time, the generated data recovery threshold voltage can be matched with the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal, thereby avoiding the problem in the prior art that when low-current leakage current tracking is used, the high current time is too long, resulting in the low current cannot be recovered. It should be noted that when the high current time is too long and the low current cannot be recovered, it specifically means that the vehicle speed digital signal cannot appear in the level state corresponding to the low current.

[0062] In one embodiment of the present invention, the data processing unit includes a threshold voltage generating unit and a signal comparing unit, wherein:

[0063] The signal comparison unit is used to compare the wheel speed voltage and the data recovery threshold voltage, and generate a corresponding wheel speed digital signal;

[0064] Based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, the threshold voltage generating unit generates a corresponding data restoration threshold voltage.

[0065] In a specific implementation, the data processing unit may include a threshold voltage generating unit and a signal comparing unit, wherein the threshold voltage generating unit may be used to generate a required data recovery threshold voltage, and the signal comparing unit may be used to compare the wheel speed voltage with the data recovery threshold voltage, and generate a corresponding wheel speed digital signal after the comparison. The specific situation of the threshold voltage generating unit and the signal comparing unit is explained below.

[0066] In one embodiment of the present invention, the threshold voltage generating unit includes a first voltage sampling unit 2, a second voltage sampling unit 3 and a comparison threshold generating circuit 4, wherein:

[0067] The first voltage sampling unit 2 and the second voltage sampling unit 3 are connected to a comparison threshold generating circuit 4, and the comparison threshold generating circuit 4 is connected to a first comparison terminal of the signal comparison unit;

[0068] The first voltage sampling unit 2 and the second voltage sampling unit 3 simultaneously receive the wheel speed voltage;

[0069] When the wheel speed voltage is in the first voltage state, and the level state of the wheel speed digital signal is the first level state, the first voltage sampling unit 2 is configured to sample and hold the wheel speed voltage, and the first sampled and held voltage generated by the sampled and held voltage is loaded to the comparison threshold generation circuit 4, and the comparison threshold generation circuit 4 generates a data recovery threshold voltage of the first state based on the first sampled and held voltage;

[0070] When the wheel speed voltage is in the second voltage state and the level state of the wheel speed digital signal is the second level state, the second voltage sampling unit 3 is configured to sample and hold the wheel speed voltage, and the second sample-and-hold voltage generated by the sampling and holding is loaded into the comparison threshold generating circuit 4. The comparison threshold generating circuit 4 generates a data recovery threshold voltage of the second state based on the second sample-and-hold voltage.

[0071] Figure 1 An embodiment of a threshold voltage generating unit is shown in the figure, in which the threshold voltage generating unit includes a first voltage sampling unit 2, a second voltage sampling unit 3 and a comparison threshold generating circuit 4, wherein the first voltage sampling unit 2 and the second voltage sampling unit 3 do not perform voltage sampling at the same time, therefore, the comparison threshold generating circuit generates a data recovery threshold voltage of a first state according to the first sampling and holding voltage, or generates a data recovery threshold voltage of a second state according to the second sampling and holding voltage.

[0072] Specifically, when the wheel speed voltage is in the first voltage state and the level state of the wheel speed digital signal is the first level state, the first voltage sampling unit 2 is configured to sample and hold the wheel speed voltage, so that the first sample-and-hold voltage can be loaded to the comparison threshold generation circuit 4. When the wheel speed voltage is in the second voltage state and the level state of the wheel speed digital signal is the second level state, the second voltage sampling unit 3 is configured to sample and hold the wheel speed voltage, so that the second sample-and-hold voltage can be loaded to the comparison threshold generation circuit 4.

[0073] In one embodiment of the present invention, when the wheel speed voltage in the first voltage state is lower than the wheel speed voltage in the second voltage state, the first level state of the wheel speed digital signal is a low level, the second level state of the wheel speed digital signal is a high level, and the data recovery threshold voltage of the second state is greater than the data recovery threshold voltage of the first state.

[0074] It can be seen from the above description that the voltage state of the wheel speed voltage is related to the wheel speed current corresponding to the output of the wheel speed sensor. When the wheel speed voltage in the first voltage state is lower than the wheel speed voltage in the second voltage state, the first level state of the wheel speed digital signal can be a low level, and at this time, the second level state of the wheel speed digital signal is a high level. In addition, the data recovery threshold voltage in the second state is greater than the data recovery threshold voltage in the first state. The specific operation of the interface circuit of the present invention is described in detail below, taking the voltage state and level state here as an example.

[0075] In one embodiment of the present invention, the signal comparison unit at least includes a voltage comparator, wherein:

[0076] The inverting terminal of the voltage comparator forms a first comparison terminal of the signal comparison unit, and the non-inverting terminal of the voltage comparator forms a second comparison terminal of the signal comparison unit;

[0077] The wheel speed voltage is loaded to the second comparison terminal of the signal comparison unit.

[0078] Figure 1 An embodiment of the signal comparison unit is shown in FIG. 1 , in which U2 is a voltage comparator, that is, a signal comparison unit is directly formed by using a voltage comparator, and WS is a wheel speed digital signal. As can be seen from the above description, the wheel speed voltage is loaded to the non-inverting terminal of the voltage comparator, and the data recovery threshold voltage is loaded to the inverting terminal of the voltage comparator. Therefore, when the voltage value of the wheel speed voltage is greater than the voltage value corresponding to the data recovery threshold voltage, the level state of the wheel speed digital signal should be a high level, otherwise, the level state of the wheel speed digital signal should be a low level.

[0079] It can be seen from the above description that the sampling states of the first voltage sampling unit 2 and the second voltage sampling unit 3 are related to the level state of the wheel speed digital signal. It can be seen that by using the level state of the wheel speed digital signal as feedback information for control, the problem of being unable to recover data in the prior art can be avoided.

[0080] In one embodiment of the present invention, the first voltage sampling unit 2 includes a voltage sampling first unit gain follower buffer, a voltage sampling first switch, a voltage sampling first resistor and a voltage sampling first capacitor, wherein:

[0081] The input end of the voltage sampling first unit gain follower buffer receives the wheel speed voltage, the output end of the voltage sampling first unit gain follower buffer is connected to one end of the voltage sampling first switch, the other end of the voltage sampling first switch is connected through one end of the voltage sampling first resistor, the other end of the voltage sampling first resistor is connected to one end of the voltage sampling first capacitor and the first input end of the comparison threshold generating circuit 4, and the other end of the voltage sampling first capacitor is grounded;

[0082] When the voltage sampling first switch is in a closed state, the first voltage sampling unit 2 samples and holds the wheel speed voltage through the voltage sampling first capacitor.

[0083] Figure 2 A schematic diagram of an embodiment of the first voltage sampling unit 2 is shown in the figure. In the figure, an operational amplifier U3 is used to form a voltage sampling first unit gain follower buffer. At this time, the inverting end of the operational amplifier U3 is connected to the output end of the operational amplifier U3, and the non-inverting end of the operational amplifier U3 is used to form the output end of the voltage sampling first unit gain follower buffer. Figure 2 S1 is a first switch for voltage sampling, and the first switch for voltage sampling can be a commonly used switch form, such as a semiconductor switch. Resistor R2 is a first resistor for voltage sampling, and capacitor C1 is a first capacitor for voltage sampling.

[0084] When the voltage sampling first switch is in a closed state, the wheel speed voltage can be loaded to the voltage sampling first capacitor through the voltage sampling first unit gain follower buffer and the voltage sampling first resistor, so as to sample and hold the wheel speed voltage using the voltage sampling first capacitor, and the generated first sampling and holding voltage can be loaded to the comparison threshold generating circuit 4.

[0085] It should be noted that the second voltage sampling unit 3 can adopt the same circuit form as the first voltage sampling unit 2, and of course, different forms can also be adopted, which can be selected according to needs. When the second voltage sampling unit 3 and the first voltage sampling unit 2 adopt the same form, the second voltage sampling unit should include a voltage sampling second unit gain follower buffer, a voltage sampling second switch, a voltage sampling second resistor and a voltage sampling second capacitor. Specifically, the corresponding conditions of the voltage sampling second unit gain follower buffer, the voltage sampling second switch, the voltage sampling second resistor and the voltage sampling second capacitor can refer to the corresponding description of the above-mentioned first voltage sampling unit 2.

[0086] Figure 3 A schematic diagram of an embodiment of the second voltage sampling unit 3 is shown in the figure. In the figure, an operational amplifier U6 is used to form a voltage sampling second unit gain follower buffer. The specific construction of the voltage sampling second unit gain follower buffer can refer to the above description; in addition, S2 is a voltage sampling second switch, R5 is a voltage sampling second resistor, and C2 is a voltage sampling second capacitor.

[0087] It should be understood that, during operation, the second voltage sampling switch and the first voltage sampling switch are not in the closed and conducting state at the same time, but in the initial state, the first voltage sampling switch should be in the closed and conducting state, that is, during the initial operation, the first voltage sampling unit 2 first performs voltage sampling, and thereafter, the signal comparison unit can compare the wheel speed voltage with the data recovery threshold voltage of the first state.

[0088] In one embodiment of the present invention, the comparison threshold generating circuit 4 includes a threshold voltage generating first subunit and a threshold voltage generating second subunit, wherein:

[0089] The first voltage sampling unit is adaptively connected to the first subunit generating the threshold voltage, and the second voltage sampling unit is adaptively connected to the second subunit generating the threshold voltage;

[0090] The first threshold voltage generating subunit generates a data recovery threshold voltage of a first state based on the first sample and hold voltage, wherein the data recovery threshold voltage of the first state is the sum of the first sample and hold voltage and the threshold adjustment voltage;

[0091] The threshold voltage generating second subunit generates a data recovery threshold voltage of a second state based on the second sample and hold voltage, wherein the data recovery threshold voltage of the second state is a difference between the second sample and hold voltage and the threshold adjustment voltage.

[0092] As can be seen from the above description, the comparison threshold generating circuit 4 generates a data recovery threshold voltage of the first state according to the first sample and hold voltage, or generates a data recovery threshold voltage of the second state according to the second sample and hold voltage. In order to meet the requirements of generating a data recovery threshold voltage of the first state and a data recovery threshold voltage of the second state, in one embodiment of the present invention, the comparison threshold generating circuit 4 may include a threshold voltage generating first subunit and a threshold generating second subunit, wherein the threshold voltage generating first subunit may generate a data recovery threshold voltage of the first state, and the threshold voltage generating second subunit may generate a data recovery threshold voltage of the second state.

[0093] In one embodiment of the present invention, when generating the data recovery threshold voltage of the first state, it is formed based on the sum of the first sample hold voltage and the threshold adjustment voltage; when generating the data recovery threshold voltage of the second state, it is formed based on the difference between the second sample hold voltage and the threshold adjustment voltage. In specific implementation, the threshold adjustment voltage is at least half of the sum of the wheel speed voltage value of the first voltage state and the vehicle speed voltage value of the second voltage state; of course, the threshold adjustment voltage can also be other situations, such as setting the threshold adjustment voltage to a value range, the center of the value range can be half of the sum of the wheel speed voltage value of the first voltage state and the vehicle speed voltage value of the second voltage state; the value range should be based on the requirements of generating a wheel speed digital signal.

[0094] In one embodiment of the present invention, the threshold voltage generating first subunit includes a voltage generating first voltage follower, a threshold adjusting first voltage unit and a threshold generating first switch, wherein:

[0095] The input end of the voltage generating first voltage follower receives the first sample and hold voltage, and the output end of the voltage generating first voltage follower is connected to the first end of the threshold generating first switch through the threshold adjusting first voltage unit;

[0096] The second end of the threshold generating first switch is connected to the first comparison end of the signal comparison unit;

[0097] When the first voltage sampling unit 2 is configured to sample and hold the wheel speed voltage, the threshold generating first switch is configured to be in a closed state at the same time, so as to load the generated first state data recovery threshold voltage to the first comparison terminal of the signal comparison unit.

[0098] Figure 4 An embodiment of the threshold voltage generating first subunit is shown in the figure. In the figure, the operational amplifier U5 can be used to generate a voltage to generate a first voltage follower. At this time, the inverting end of the operational amplifier U5 is connected to the output end of the operational amplifier U5, and the non-inverting end of the operational amplifier U5 forms the input end of the voltage generating first voltage follower. Figure 1 , Figure 4 and Figure 5 In the example, Vs_1 is the first sampling and holding voltage. Figure 4 In the embodiment, S3 is a threshold value generating first switch, and the threshold value generating first switch may be a semiconductor switch. Figure 4 An embodiment of a threshold adjustment first voltage unit is also shown. In the figure, the threshold adjustment first voltage unit includes a current source Δith and a resistor R4. At this time, the output end of the voltage-generating first voltage follower is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the output end of the current source Δith and the first end of the threshold-generating first switch.

[0099] It can be understood that the threshold adjustment voltage generated by the threshold adjustment first voltage unit is configured to generate a first switch in a closed conductive state only when the first voltage sampling unit 2 is configured to sample and hold the wheel speed voltage and after the first sample and hold voltage is stable. At this time, a data recovery threshold voltage of the first state can be generated based on the first sample and hold voltage and the threshold adjustment voltage. Figure 4 In the example, Vth_1 is the data recovery threshold voltage of the first state.

[0100] The second subunit for generating the threshold voltage may be in the same form as the first subunit for generating the threshold voltage, or may be in different forms. Figure 4An embodiment of a second subunit for generating a threshold voltage is also shown. As can be seen from the figure, the second subunit for generating a threshold voltage adopts a similar form to the first subunit for generating a threshold voltage. The difference is that the threshold adjustment voltage is different so as to generate a corresponding data recovery threshold voltage of the second state.

[0101] Specifically, the threshold voltage generating second subunit includes a voltage generating second voltage follower, a threshold adjusting second voltage unit and a threshold generating second switch. Figure 4 In the figure, an operational amplifier U4 can be used to form a voltage-generating second voltage follower, S4 is a threshold-generating second switch, and the threshold-adjusting second voltage unit includes a current source Δith and a resistor R3, wherein the output end of the voltage-generating second voltage follower is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the current source Δith and a first end of the threshold-generating second switch, the other end of the current source Δith is grounded, and the first end of the threshold-generating second switch is connected to the first comparison end of the signal comparison unit.

[0102] The method of generating the second sub-unit by the threshold voltage may refer to the corresponding description of the first sub-unit by the threshold voltage. Figure 4 In the embodiment, Vth_h is the data recovery threshold voltage of the first state. In the specific implementation, the current source Δith is preferably a constant current source, and the output current value is the same, and the resistance value of the resistor R3 and the resistor R4 is also equal, and both are R.

[0103] Combine the following Figure 5 The working process of the interface circuit of the present invention is described.

[0104] Depend on Figure 5 It can be seen that after the wheel speed sensor is powered on, the wheel speed current increases from 0 to a low current value il, and the wheel speed voltage of the first voltage state can be converted by the current-to-voltage conversion unit 1. Figure 5 In the figure, v1 is the wheel speed voltage in the first voltage state. As can be seen from the above description, the voltage sampling first switch in the first voltage sampling unit 2 is in a closed conduction state. At this time, the voltage value of the first sampled and held voltage will be stabilized as the wheel speed voltage in the first voltage state. Then, the first subunit can generate a data recovery threshold voltage in the first state through the threshold voltage generation. Figure 5 In the figure, Vth_1 is the data recovery threshold voltage of the first state, and Vth_1 should be vl+Δith*R, Vs_1 is the first sample hold voltage, and idata is the wheel speed current.

[0105] From the above description, it can be seen that only when the first sample and hold voltage stabilizes to the wheel speed voltage of the first voltage state, the threshold is configured to generate the first switch closure. At this time, the first subunit can generate the data recovery threshold voltage of the first state through the threshold voltage generation.

[0106] When the wheel speed current switches from low current il to high current ih, the wheel speed digital signal should change from low level to high level. It can be understood that after a time th, the wheel speed current will stabilize at high current ih. At this time, the second switch of the voltage sampling is configured to be in a closed and conductive state, and the first switch of the voltage sampling is configured to be in an open state. At this time, the first sampling and holding voltage stored in the first capacitor of the voltage sampling will slowly decrease due to the leakage of the capacitor, but because the threshold generation first switch remains in a closed and conductive state, at this time, the data recovery threshold voltage of the first state will still be generated, but the data recovery threshold voltage of the first state will gradually decrease.

[0107] When the voltage sampling second switch is in the closed and conducting state, the second sampling and holding voltage can be generated by the second voltage sampling unit 3, and the second sampling and holding voltage is loaded into the threshold voltage generating second subunit. After the time th_u has passed, the second sampling and holding voltage will stabilize as the wheel speed voltage of the second voltage state. At this time, the threshold generating second switch is configured to be closed and conducting, and the threshold voltage generating second subunit can generate the data of the second state to restore the threshold voltage. Figure 5 In the example, Vs_h is the second sampling and holding voltage, and Vth_h is the data recovery threshold voltage of the second state. In addition, the data recovery threshold voltage of the second state is vh-Δith*R.

[0108] During operation, the wheel speed current may switch from a high current ih to a low current il. The current-voltage conversion unit 1, the first voltage sampling unit 2, the second voltage sampling unit 3, and the comparison threshold generating circuit 4 work in coordination, and the above description may be referred to, so that all wheel speed currents can be converted into corresponding wheel speed digital signals. For example, when switching to a low current il, the vehicle flow speed current will stabilize to a low current il after a time tl, and at this time, a stable vehicle flow speed voltage vl can be obtained. During this process, the voltage sampling first switch is in a closed conduction state, and the comparison threshold generating circuit 4 provides a data recovery threshold voltage of a second state. When the first sampling holding voltage stabilizes to a wheel speed voltage of a second voltage state after a time th_1, the configuration threshold generating first switch is closed, and the threshold generating second switch is disconnected, so that the threshold voltage generating first subunit can generate a data recovery threshold voltage of a first state.

[0109] In order to avoid frequent switching of the current comparison threshold, it can also be defined that only when the high current value ih lasts for more than a certain time, the data recovery threshold voltage of the first state is switched to the data recovery threshold voltage of the second state. The duration of the high current value ih can be determined according to the normal high current duration of the wheel speed sensor, such as 2mS. In addition, the time th, the time tl, the time th_u, and the time th_l are all determined according to the working parameters of the wheel speed sensor, and the specific situation is consistent with the existing.

[0110] In summary, a data recovery method suitable for a vehicle speed sensor can be obtained. In one embodiment of the present invention, for any wheel speed sensor, the interface circuit described above is used to connect and cooperate with the wheel speed sensor, so that the speed information detected by the wheel speed sensor is processed by the interface circuit to generate a corresponding wheel speed digital signal.

[0111] Specifically, the method of generating the wheel speed digital signal by using the interface circuit can refer to the above description. It can be understood that when the above interface circuit is working, the switch state control of the second switch generated by the above threshold can be controlled by the ECU or MCU receiving the wheel speed digital signal.

Claims

1. An interface circuit suitable for a wheel speed sensor, characterized in that: The interface circuit comprises: A current-voltage conversion unit is adapted to be connected with the wheel speed sensor, provides working power to the wheel speed sensor, and converts the wheel speed current output by the wheel speed sensor into a corresponding wheel speed voltage; A data processing unit is adaptively connected to the current-voltage conversion unit and is used to generate a wheel speed digital signal corresponding to the wheel speed voltage, wherein: When generating the wheel speed digital signal, the wheel speed voltage is compared with the data recovery threshold voltage to generate the wheel speed digital signal based on the comparison state of the wheel speed voltage and the data recovery threshold voltage; The data recovery threshold voltage is generated based on at least the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, wherein: The voltage state of the wheel speed voltage includes at least a first voltage state and a second voltage state; When the wheel speed voltage switches between the first voltage state and the second voltage state, a corresponding data recovery threshold voltage is generated based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, so that the generated data recovery threshold voltage matches the voltage state of the current wheel speed voltage and the level state of the wheel speed digital signal.

2. The interface circuit for a wheel speed sensor according to claim 1, characterized in that: The data processing unit includes a threshold voltage generating unit and a signal comparing unit, wherein: The signal comparison unit is used to compare the wheel speed voltage and the data recovery threshold voltage, and generate a corresponding wheel speed digital signal; Based on the voltage state of the wheel speed voltage and the level state of the wheel speed digital signal, the threshold voltage generating unit generates a corresponding data restoration threshold voltage.

3. The interface circuit for a wheel speed sensor according to claim 2, characterized in that: The threshold voltage generating unit includes a first voltage sampling unit, a second voltage sampling unit and a comparison threshold generating circuit, wherein: The first voltage sampling unit and the second voltage sampling unit are connected to a comparison threshold generating circuit, and the comparison threshold generating circuit is connected to a first comparison terminal of the signal comparison unit; The first voltage sampling unit and the second voltage sampling unit simultaneously receive the wheel speed voltage; When the wheel speed voltage is in a first voltage state and the level state of the wheel speed digital signal is a first level state, a first voltage sampling unit is configured to sample and hold the wheel speed voltage, and a first sampled and held voltage generated by the sampled and held voltage is loaded into a comparison threshold generation circuit, and the comparison threshold generation circuit generates a data recovery threshold voltage of a first state based on the first sampled and held voltage; When the wheel speed voltage is in the second voltage state and the level state of the wheel speed digital signal is the second level state, a second voltage sampling unit is configured to sample and hold the wheel speed voltage, and a second sample-and-hold voltage generated by the sample-and-hold is loaded into a comparison threshold generation circuit, and the comparison threshold generation circuit generates a data recovery threshold voltage of the second state based on the second sample-and-hold voltage.

4. The interface circuit for a wheel speed sensor according to claim 3, characterized in that: When the wheel speed voltage in the first voltage state is lower than the wheel speed voltage in the second voltage state, the first level state of the wheel speed digital signal is a low level, the second level state of the wheel speed digital signal is a high level, and the data recovery threshold voltage in the second state is greater than the data recovery threshold voltage in the first state.

5. The interface circuit for a wheel speed sensor according to claim 4, characterized in that: The first voltage sampling unit includes a voltage sampling first unit gain follower buffer, a voltage sampling first switch, a voltage sampling first resistor and a voltage sampling first capacitor, wherein: The input end of the voltage sampling first unit gain follower buffer receives the wheel speed voltage, the output end of the voltage sampling first unit gain follower buffer is connected to one end of the voltage sampling first switch, the other end of the voltage sampling first switch is connected through one end of the voltage sampling first resistor, the other end of the voltage sampling first resistor is connected to one end of the voltage sampling first capacitor and the first input end of the comparison threshold generating circuit, and the other end of the voltage sampling first capacitor is grounded; When the voltage sampling first switch is in a closed state, the first voltage sampling unit samples and holds the wheel speed voltage through the voltage sampling first capacitor.

6. The interface circuit for a wheel speed sensor according to claim 4, characterized in that: The comparison threshold generating circuit includes a threshold voltage generating first subunit and a threshold voltage generating second subunit, wherein: The first voltage sampling unit is adaptively connected to the first subunit generating the threshold voltage, and the second voltage sampling unit is adaptively connected to the second subunit generating the threshold voltage; The first threshold voltage generating subunit generates a data recovery threshold voltage of a first state based on the first sample and hold voltage, wherein the data recovery threshold voltage of the first state is the sum of the first sample and hold voltage and the threshold adjustment voltage; The threshold voltage generating second subunit generates a data recovery threshold voltage of a second state based on the second sample and hold voltage, wherein the data recovery threshold voltage of the second state is a difference between the second sample and hold voltage and the threshold adjustment voltage.

7. The interface circuit for a wheel speed sensor according to claim 6, characterized in that: The threshold voltage generating first subunit includes a voltage generating first voltage follower, a threshold adjusting first voltage unit and a threshold generating first switch, wherein: The input end of the voltage generating first voltage follower receives the first sample and hold voltage, and the output end of the voltage generating first voltage follower is connected to the first end of the threshold generating first switch through the threshold adjusting first voltage unit; The second end of the threshold generating first switch is connected to the first comparison end of the signal comparison unit; When the first voltage sampling unit is configured to sample and hold the wheel speed voltage, the threshold generating first switch is configured to be in a closed state at the same time, so as to load the generated first state data recovery threshold voltage to the first comparison terminal of the signal comparison unit.

8. The interface circuit for a wheel speed sensor according to claim 6, characterized in that: The threshold adjustment voltage is at least half of the sum of the wheel speed voltage value in the first voltage state and the vehicle speed voltage value in the second voltage state.

9. The interface circuit for a wheel speed sensor according to any one of claims 3 to 8, characterized in that: The signal comparison unit at least includes a voltage comparator, wherein: The inverting terminal of the voltage comparator forms a first comparison terminal of the signal comparison unit, and the non-inverting terminal of the voltage comparator forms a second comparison terminal of the signal comparison unit; The wheel speed voltage is loaded to the second comparison terminal of the signal comparison unit.

10. A data recovery method for a vehicle speed sensor, characterized in that: For any wheel speed sensor, an interface circuit as described in any one of claims 1 to 9 is used to connect and cooperate with the wheel speed sensor, so that the interface circuit processes the speed information detected by the wheel speed sensor to generate a corresponding wheel speed digital signal.

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