A touch capacitance detection circuit

Abstract

The utility model discloses a touch capacitance detection circuit, including: an RC oscillation circuit, which includes: an RC network operational amplifier, whose input end is connected to an RC series-parallel frequency network; a Touch equivalent RC network, which is connected to the output end of the RC network operational amplifier; a pre-operational amplifier, whose input end is connected to the Touch equivalent RC network; an optocoupler isolation output circuit, which realizes the conversion between analog signals and digital signals. An active filter and rectifier filter circuit module improves the anti-interference ability. A comparison circuit output module improves the sensitivity. The touch capacitance detection circuit provided by the utility model has a simple structure, is independent of algorithms, has stable signals, strong anti-interference ability, high sensitivity, and can quickly detect touch capacitance.

Description

Technical Field

[0001] The utility model belongs to the technical field of touch buttons, and particularly relates to a touch capacitance detection circuit. Background Art

[0002] With the rapid development of the automobile market, the configuration of automobiles is also being updated day by day. The buttons on the steering wheel of automobiles are gradually changing from traditional mechanical buttons to electronic touch buttons. Touch buttons have gradually become the standard configuration of new automobiles. This puts forward higher requirements on the functions of touch buttons. It is necessary to realize the traditional button functions and meet the driver's safe operation and realize touch prevention. The core of the touch membrane button is the detection of capacitance. In this case, the detection of touch capacitance is particularly important.

[0003] Capacitive touch buttons are based on the principle of self-capacitance: when a finger approaches the button area, the equivalent capacitance of the button area increases, that is, the self-capacitance of the button area increases. The self-capacitance detection chip detects whether the self-capacitance changes to determine whether a touch event occurs.

[0004] Although touch buttons are currently on the market, the touch capacitance detection method generally uses dedicated digital ICs, and the capacitance detection is achieved through complex software algorithms. By detecting the oscillator frequency or period related to the self-capacitance, it is determined whether there is a finger touch. When a finger touches, the oscillator frequency is reduced, and the oscillator output square wave is counted within a reference clock cycle to detect the occurrence of a touch event. This solution is simple to operate and has low power consumption, but it is easily interfered with. Parameters such as the capacitance detection threshold are highly dependent on the software algorithm, and a lot of time is spent on software debugging. This not only has high requirements for the coordination of software and hardware, but also requires more precision for manual debugging, which is time-consuming and labor-intensive. The capacitance detection anti-interference ability of the integrated IC is weak. Utility Model Content

[0005] The touch capacitance detection circuit provided by the utility model has a simple structure, is independent of algorithms, has stable signals, strong anti-interference capability, high sensitivity, and can quickly detect touch capacitance.

[0006] The technical solution provided by the utility model is:

[0007] A touch capacitance detection circuit, comprising:

[0008] An RC network operational amplifier, the input of which is connected to an RC series-parallel frequency network;

[0009] Touch equivalent RC network, which is connected to the output end of the RC network operational amplifier;

[0010] A preamplifier, whose input is connected to the Touch equivalent RC network;

[0011] Active filtering and rectifier filtering circuit modules;

[0012] Comparison circuit output module;

[0013] Optocoupler isolation output circuit, which realizes the conversion between analog signal and digital signal.

[0014] Preferably, the pre-operational amplifier is an MCP6497T operational amplifier.

[0015] Preferably, the optical coupler isolation output circuit adopts a VO617A model low input current optical isolator.

[0016] Preferably, the active filtering and rectifying filtering circuit module comprises:

[0017] RC series-parallel filtering network is used to maintain the circuit output frequency;

[0018] A filtering operational amplifier is connected to an RC series-parallel filtering network to improve the circuit's anti-interference capability.

[0019] RC series-parallel rectifier network is used in the circuit to rectify the AC signal from the upper level;

[0020] The rectifier operational amplifier is connected to the RC series-parallel rectifier network and can convert AC signals into DC signals for output.

[0021] Preferably, the comparison circuit module includes:

[0022] Two voltage divider resistors;

[0023] Comparator operational amplifier;

[0024] By adjusting the voltage-dividing size of the two voltage-dividing resistors, the threshold of this part can be adjusted to achieve sensitivity adjustment.

[0025] Preferably, the two voltage-dividing resistors are 10K resistors.

[0026] The beneficial effects of the utility model are:

[0027] The touch capacitance detection circuit provided by the utility model has a simple structure, is independent of algorithms, has stable signals, strong anti-interference capability, high sensitivity, and can quickly detect touch capacitance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the touch capacitance detection circuit described in the present utility model.

[0029] Figure 2 This is an active filter circuit module of the touch capacitance detection circuit described in the utility model.

[0030] Figure 3 It is a rectifier filter circuit and a comparison circuit module of the touch capacitance detection circuit described in the utility model.

[0031] Figure 4 This is an optocoupler isolation output circuit of the touch capacitance detection circuit described in the utility model. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0033] like Figure 1 As shown, the utility model provides a touch capacitance detection circuit, which includes an RC network operational amplifier, whose input end is connected to the RC series-parallel frequency network; a Touch equivalent RC network, which is connected to the output end of the RC network operational amplifier; a preamplifier, whose input end is connected to the Touch equivalent RC network; an active filter circuit module, which is connected to the preamplifier to improve the anti-interference ability of the circuit; a rectifier filter circuit module, which is connected to the active filter circuit module; a comparison circuit module, which is connected to the rectifier filter circuit module; and an optocoupler isolation output circuit module, which realizes the conversion between analog signals and digital signals.

[0034] like Figure 2 As shown, the utility model provides a touch capacitance detection circuit, and the active filter circuit module includes:

[0035] RC series-parallel filtering network is used to maintain the circuit output frequency;

[0036] A filtering operational amplifier is connected to an RC series-parallel filtering network to improve the circuit's anti-interference capability.

[0037] like Figure 3 As shown, the utility model provides a touch capacitance detection circuit, and the rectification and filtering circuit module includes:

[0038] RC series-parallel rectifier network is used in the circuit to rectify the AC signal from the upper level;

[0039] The rectifier operational amplifier is connected to the RC series-parallel rectifier network and can convert AC signals into DC signals for output.

[0040] like Figure 3 As shown, the utility model provides a touch capacitance detection circuit, and the comparison circuit module includes: two voltage-dividing resistors and a comparison operational amplifier;

[0041] Among them, the two voltage divider resistors are 10K resistors.

[0042] By adjusting the voltage-dividing size of the two voltage-dividing resistors, the threshold of this part can be adjusted to achieve sensitivity adjustment.

[0043] This part rectifies the AC signal from the upper stage and uses the rectified signal as the signal input with the fixed threshold of the comparator. The threshold of this part is adjusted to achieve sensitivity adjustment. That is, the voltage divided by R131 and R132.

[0044] The optocoupler isolation output circuit uses a VO617A model low input current optocoupler. This series of low input current optocouplers, with phototransistor outputs, protects equipment users from electric shocks and prevents microprocessors within these systems from being damaged by voltage spikes.

[0045] An MCU microcontroller unit is installed inside the car. After the optocoupler isolation output circuit realizes signal conversion, the MCU will capture the logic level and detect the high and low levels.

[0046] A touch capacitance detection circuit uses a multi-stage operational amplifier to amplify, filter, rectify, and comparator digital signals. The charging and discharging process of the RC network and the positive feedback effect generate a stable TP1 sinusoidal AC signal; then it passes through the Touch equivalent RC network pre-follower amplifier. The MCU only needs to detect the high and low levels to identify whether the touch button is pressed. The capacitance detection implemented by the pure analog circuit eliminates the need for complex software algorithms, so that the capacitance threshold adjustment is completed by the hardware circuit parameter setting, thereby avoiding the BUG in the software algorithm and having better flexibility.

[0047] Although the implementation scheme of the utility model has been disclosed as above, it is not limited to the applications listed in the specification and implementation modes. It can be fully applied to various fields suitable for the utility model. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A touch capacitance detection circuit, characterized in that: include: An RC network operational amplifier, the input of which is connected to an RC series-parallel frequency network; Touch equivalent RC network, which is connected to the output end of the RC network operational amplifier; A preamplifier, whose input is connected to the Touch equivalent RC network; Active filtering and rectifier filtering circuit modules; Comparison circuit output module; Optocoupler isolation output circuit, which realizes the conversion between analog signal and digital signal.

2. The touch capacitance detection circuit according to claim 1, characterized in that: The preamplifier is an MCP6497T amplifier.

3. The touch capacitance detection circuit according to claim 1, characterized in that: The optical coupler isolation output circuit adopts a VO617A model low input current optical isolator.

4. The touch capacitance detection circuit according to claim 1, characterized in that: The active filtering and rectifying filtering circuit module comprises: RC series-parallel filtering network is used to maintain the circuit output frequency; A filter operational amplifier connected to an RC series-parallel filter network; RC series-parallel rectifier network is used in the circuit to rectify the AC signal from the upper level; The rectifier operational amplifier is connected to the RC series-parallel rectifier network and can convert AC signals into DC signals for output.

5. The touch capacitance detection circuit according to claim 1, characterized in that: The comparison circuit output module comprises: Two voltage divider resistors; Comparator operational amplifier; By adjusting the voltage-dividing size of the two voltage-dividing resistors, the threshold of this part can be adjusted to achieve sensitivity adjustment.

6. The touch capacitance detection circuit according to claim 5, characterized in that: The two voltage-dividing resistors are 10K resistors.

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