Two-wire capacitive door handle switch detection system

Abstract

The application discloses a two-wire capacitive door handle switch detection system, which comprises a capacitive switch and a keyless entry system, the capacitive switch comprises an LDO, an MCU, a capacitive sensor and an output triode, the capacitive sensor comprises two different touch areas for detecting unlocking and locking, the capacitive sensor is connected with the MCU, the square wave signal output end of the MCU is connected with the base of the output triode, the emitter of the output triode is grounded, and the collector is connected with the hardware detection circuit of the keyless entry system through a resistor R2 and a switch diode, and the LDO supplies power for the MCU. The capacitive door handle switch adopts the change of the detection capacitance to judge whether the key is triggered or not, and does not need the physical pressing of the stroke; the user experience is improved, meanwhile, the capacitive switch can be arranged with the sensing area on the inner side of the door handle, which is used for detecting the operation of the user stretching the hand to pull the door, and executing the unlocking of the vehicle, and the use experience is further improved.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic control technology. Background Technology

[0002] The market demand for intelligent vehicles is driving the increasing adoption of keyless entry systems. Traditional keyless entry systems use push-button door handles, where the vehicle is locked or unlocked by pressing a physical button on the door handle. Since physical buttons require force to activate, the user experience is poor. Furthermore, the push-button action necessitates drilling holes in the door handle, compromising its aesthetics and overall design.

[0003] In addition, physical buttons are very likely to freeze in the winter in northern regions due to their small size, making them impossible to press and unlock. This causes inconvenience to unlocking the vehicle. In particular, the current trend of using hidden door handles in vehicles makes it difficult to arrange buttons when these handles are small. This not only affects the overall aesthetics of the handle but also makes the operation less user-friendly. Summary of the Invention

[0004] The technical problem to be solved by this invention is to realize a capacitive door handle switch that detects changes in capacitance to determine whether a button is triggered, without requiring physical travel for pressing.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a two-wire capacitive door handle switch detection system, comprising a capacitive switch and a keyless entry system. The capacitive switch includes an LDO, an MCU, a capacitive sensor, and an output transistor. The capacitive sensor includes two different touch areas for detecting unlocking and locking. The capacitive sensor is connected to the MCU. The square wave signal output terminal of the MCU is connected to the base of the output transistor. The emitter of the output transistor is grounded, and the collector is connected to the hardware detection circuit of the keyless entry system via a resistor R2 and a switching diode. The LDO powers the MCU.

[0006] A pull-up resistor R1 is connected to the input line of the capacitive switch to the hardware detection circuit of the keyless entry system.

[0007] The other end of the pull-up resistor R1 is connected to the power supply VBAT_D inside the keyless entry system. The power supply inside the keyless entry system is provided by the car battery. VBAT_D supplies power to the capacitive switch through the pull-up resistor R1.

[0008] The hardware detection circuit is a square wave detection circuit unit, which is used to process the square wave signal on the power line and convert it into a square wave signal that the MCU can directly recognize.

[0009] The hardware detection circuit includes a small-signal PMOS, which detects V... GS ≤V GSt When h is reached, the PMOS transistor is turned on. At this time, VBAT_D is input to the MCU port after being divided by resistors R3 and R4. When V... GS >V GSth When PMOS is turned off, the MCU port detects a low level.

[0010] The pull-up resistor inside the keyless entry system is used to power the two-wire capacitive switch and sample signals. The resistance of resistor R2 is 470Ω and the resistance of pull-up resistor R1 is 200Ω.

[0011] After the power supply enters the inside of the capacitor switch, it is input to the LDO through diode D2. The LDO is a linear regulated power supply.

[0012] The system has three working modes:

[0013] In Mode 1, neither the unlocking nor de-locking regions were triggered.

[0014] Mode 2: Unlocking triggers in any region, but does not drive the output transistor to conduct;

[0015] Mode 3: Unlocking triggers any region, simultaneously driving the output transistor to conduct.

[0016] Mode 1 and Mode 2 are low-current operating states, where the pull-up resistor generates a small voltage drop, and the hardware detection circuit switches to a low level; in Mode 3, the pull-up resistor generates a large voltage drop, and the hardware detection circuit switches to a high level.

[0017] The capacitive door handle switch of this invention uses changes in capacitance to determine whether to trigger the button, eliminating the need for physical pressing. This improves the user experience. In addition, the capacitive switch can have a sensing area arranged on the inside of the door handle to detect the user's hand reaching out to pull the door and unlock the vehicle, further enhancing the user experience.

[0018] Capacitive door handle switches typically define two sensing areas: unlock and lock. The switch also requires an internal MCU to acquire and process signals, thus requiring four pins for output: power, ground, unlock output, and lock output. However, a two-wire capacitive switch solution directly couples the signal to the power line, reducing the overall system cost. Attached Figure Description

[0019] The following is a brief explanation of the content represented by each figure in this specification:

[0020] Figure 1 Block diagram of a two-wire capacitive door handle system

[0021] Figure 2 This is a hardware detection circuit diagram. Detailed Implementation

[0022] The following description, with reference to the accompanying drawings, details the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0023] Two-wire capacitive switches have only two external interfaces: power and ground. They are trigger-lock / unlock type, meaning the capacitive switch drives the internal transistor to turn on and off according to a defined frequency or protocol. This invention, based on the different operating modes of the capacitive switch, uses a simple discrete device to convert occasional square wave signals on the power supply line into square wave signals that can be recognized by the MCU.

[0024] Capacitive door handle switches typically define two sensing areas: unlock and lock. The switch also requires an internal MCU to acquire and process signals, thus requiring four pins for output: power, ground, unlock output, and lock output. However, a two-wire capacitive switch solution directly couples the signal to the power line, reducing the overall system cost.

[0025] The two-wire capacitive door handle switch detection system includes: a two-wire capacitive door handle switch with two touch areas: an unlock touch area and a lock touch area. Touching either area generates two square wave signals of different frequencies or protocols on the switch's power supply line; a hardware detection circuit unit (square wave detection circuit unit) converts the square wave signal superimposed on the handle's power supply line into a square wave signal that the MCU can directly acquire. The MCU identifies the converted square wave signal and distinguishes between an unlock signal input and a lock signal input.

[0026] The two-wire capacitive switch is powered through the keyless entry system and internally includes a power supply system (LDO), an MCU, a capacitive sensor, and an output transistor. When the MCU detects the input from the capacitive sensor, it drives the transistor to turn on or off to generate a square wave.

[0027] The square wave detection circuit unit processes the square wave signal on the power line and converts it into a square wave signal that the MCU can directly recognize. The keyless entry system supplies power to the two-wire capacitive door handle switch through a suitable pull-up resistor. When the capacitive handle switch is working, it drives the transistor at the port to turn on or off. At this time, different voltage drops will be generated across the pull-up resistor of the keyless entry system. The square wave detection circuit unit converts the voltage drop across the pull-up resistor into a square wave signal that the MCU can directly recognize.

[0028] like Figure 2 This is a system block diagram for a two-wire capacitive switch scheme. The power supply for the capacitive switch is provided by the keyless entry system. VBAT_D is the internal power supply for the keyless entry system, which is provided by the car battery. VBAT_D supplies power to the capacitive switch through R1.

[0029] The internal system design of the capacitive switch is as follows: After the power supply enters the internal capacitive switch, it is input to the LDO through diode D2. The LDO is a linear regulated power supply, ensuring that the internal MCU and other components of the capacitive switch operate within the required range. The main function of transistor Q1 is to generate a square wave, and a resistor R2 is connected in series with the emitter of the transistor. The function of R2 is to ensure that when transistor Q1 is turned on, the supply voltage at the port is not pulled down to 0V, which would cause the capacitive switch to fail to work due to lack of power. Therefore, R2 cannot be too small; at the same time, R2 cannot be too large, otherwise the voltage drop across R1 will be too small, and the voltage drop across R1 when the transistor is turned on will not be effectively detected.

[0030] Q2 is a small-signal PMOS, when V GS ≤V GSth When the PMOS is turned on, VBAT_D is divided by resistors R3 and R4 and enters the MCU port, where it can be effectively recognized as an external high level. When V GS >V GSth When PMOS is turned off, the MCU port detects a low level.

[0031] Capacitive switches operate in three modes:

[0032] In Mode 1, neither the latch-up nor unlock-down regions are triggered. The capacitive switch operates in low-power mode, with a static power consumption of approximately 100-200uA. In this example, resistor R1 is selected as 200 ohms. The voltage drop across this resistor is 0.04V, far below the PMOS turn-on voltage, causing the MCU port to detect a low level.

[0033] Mode 2: Triggering in any region of the lockout, but without driving the transistor to conduct. At this time, the capacitor switch is in non-low power mode, but the operating current is small, generally not exceeding 5mA; for example, resistor R1 is selected as 200 ohms, and the voltage drop across this resistor is 1V; the turn-on voltage of the PMOS is not reached, and the MCU port detects a low level.

[0034] Mode 3: Triggering in any region simultaneously drives the transistor to conduct, resulting in a larger operating current. Based on the example where R1 is 200 ohms, R2 is 470 ohms, and the minimum voltage is 9V, the voltage across R1 exceeds the PMOS's turn-on voltage. At this point, the PMOS conducts, and the MCU port detects a high level.

[0035] Define the trigger unlocking region to drive the transistor according to different frequencies or protocols, and couple the frequency or protocol signal to the power supply line through the voltage divider of resistors R1 and R2; at the same time, the frequency or protocol signal coupled on the power supply line is converted into a frequency or protocol signal that can be directly recognized by the MCU port through the above-mentioned hardware detection circuit.

[0036] The door handle's locking / unlocking output is distinguished by frequency.

[0037] The three modes exhibit two states when passing through the hardware detection circuit: Mode 1 and Mode 2 are low-current operating states, the transistor is not conducting, and the voltage drop across the power supply pull-up resistor is small, so the hardware detection circuit switches to a low level; when Mode 3 is operating, the transistor is conducting, the operating current is large, and the voltage drop across the pull-up resistor is large, so the hardware detection circuit switches to a high level.

[0038] The pull-up resistor inside the keyless entry system is used for both powering the two-wire capacitive switch and sampling the signal. Therefore, the pull-up resistor needs to be matched with the two-wire capacitive switch interface to ensure that the port voltage after the voltage drop across the resistor when the transistor is conducting can still guarantee the normal operation of the two-wire capacitive switch; at the same time, the voltage drop across the resistor can be correctly converted to either 0 or 1 level.

[0039] This invention enables the identification of the unlocking and locking areas of a door handle switch using only two wires: power and ground. The hardware detection circuit is simple, requiring only basic components to convert the square wave signal. When the capacitive door handle switch is touched to unlock or lock, the MCU inside the switch drives the transistor on its port to turn on and off, generating a square wave on the power line. The keyless entry system then uses a corresponding hardware detection circuit to convert this square wave signal into a square wave signal that the internal MCU can directly recognize. When the unlocking or locking area is triggered, the square wave frequency or protocol generated on the power line differs, resulting in a different frequency or protocol converted by the hardware detection circuit within the keyless entry system. The MCU inside the keyless entry system can identify these different frequencies or protocols and, based on a predefined frequency or protocol, distinguish between the unlocked and locked areas.

[0040] The present invention has been described above with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A two-wire capacitive door handle switch detection system, characterized in that: The system includes a capacitive switch and a keyless entry system. The capacitive switch includes an LDO, an MCU, a capacitive sensor, and an output transistor. The capacitive sensor includes two different touch areas for detecting unlocking and locking. The capacitive sensor is connected to the MCU. The square wave signal output terminal of the MCU is connected to the base of the output transistor. The emitter of the output transistor is grounded, and the collector is connected to the hardware detection circuit of the keyless entry system via a resistor R2 and a switching diode. The LDO powers the MCU. A pull-up resistor R1 is connected to the input line of the capacitive switch to the hardware detection circuit of the keyless entry system. The other end of the pull-up resistor R1 is connected to the power supply VBAT_D inside the keyless entry system. The power supply inside the keyless entry system is provided by the car battery. The VBAT_D supplies power to the capacitive switch through the pull-up resistor R1. The hardware detection circuit is a square wave detection circuit unit, which is used to process the square wave signal on the power line and convert it into a square wave signal that the MCU can directly recognize. The hardware detection circuit includes a small-signal PMOS, which detects V... GS ≤V GSt When h is reached, the PMOS transistor is turned on. At this time, VBAT_D is input to the MCU port after being divided by resistors R3 and R4. When V... GS >V GSth When PMOS is turned off, the MCU port detects a low level.

2. The two-wire capacitive door handle switch detection system according to claim 1, characterized in that: The pull-up resistor inside the keyless entry system is used to power the two-wire capacitive switch and sample signals. The resistance of resistor R2 is 470Ω and the resistance of pull-up resistor R1 is 200Ω.

3. The two-wire capacitive door handle switch detection system according to claim 2, characterized in that: After the power supply enters the inside of the capacitor switch, it is input to the LDO through diode D2. The LDO is a linear regulated power supply.

4. The two-wire capacitive door handle switch detection system according to claim 3, characterized in that: The system has three working modes: In Mode 1, neither the unlocking nor de-locking regions were triggered. Mode 2: Unlocking triggers in any region, but does not drive the output transistor to conduct; Mode 3: Unlocking triggers any region, simultaneously driving the output transistor to conduct.

5. The two-wire capacitive door handle switch detection system according to claim 4, characterized in that: Mode 1 and Mode 2 are low-current operating states, where the pull-up resistor generates a small voltage drop, and the hardware detection circuit switches to a low level; in Mode 3, the pull-up resistor generates a large voltage drop, and the hardware detection circuit switches to a high level.

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