High sensitivity touch button circuit

Abstract

The invention discloses a high-sensitivity touch key circuit; the high-sensitivity touch key circuit comprises a touch circuit and a charge transfer circuit, the touch circuit comprises a left channel key KL1 and a right channel key KR1, the left channel key KL1 comprises a left channel key port parasitic capacitor C PL1 , left channel button finger touch capacitance C fL1 , left channel button switch S1L1, button internal charging switch S2L1, the button internal charging switch S2L1 is electrically connected to a main control chip, the right channel button KR1 has the same structure as the left channel button KL1; the charge transfer circuit includes a sub-control chip, the sub-control chip is electrically connected to a switch S2 and a switch S3; the present invention reduces the influence of parasitic capacitance, improves touch sensitivity, and proposes a distributed charge transfer structure, which eliminates the influence of parasitic capacitance when the number of buttons is large and the peripheral reference capacitance is small.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic products, and in particular relates to a high-sensitivity touch key circuit. Background Art

[0002] Electronic technology is developing very rapidly now. In order to make it more convenient for us to use electronic products, many products use touch buttons as a medium for human-computer interaction. Commonly used touch buttons can be divided into two categories: resistive and capacitive. The most widely used is capacitive touch buttons. The principle of resistive touch buttons is that the human body presses the resistor, causing the resistor size to change. The change in resistance is the change of the entire circuit signal, thereby achieving the control effect. However, there is a major defect, that is, after a long time, the resistor must be correctly identified by a greater pressure, which leads to this technology being gradually eliminated. The principle of capacitive touch buttons is that when the human body approaches the capacitive button, the current generated by the human body is coupled to the static capacitor, thereby increasing the capacitance value of the button. The change in capacitance value is judged by the internal working circuit of the chip, and this change is converted into a digital signal to achieve the purpose of controlling the electronic device. Capacitive touch buttons are generally divided into two types, one of which is based on an oscillator-type structure; the other is a charge-discharge structure based on charge transfer. However, various touch buttons on the market still have various problems.

[0003] For example, the capacitive touch button detection circuit disclosed in the authorization announcement number CN110176922A realizes the overall structural design of the capacitive touch button detection circuit ingeniously, the structure is simple, reasonable and stable, easy to implement and low in manufacturing cost. By using a clock generation circuit combined with an inverter to periodically control the switch states of the first to third control switches, the detection circuit is alternately operated in the circuit self-correction stage and the capacitance detection stage, thereby effectively improving the stability of the performance parameters of the circuit and enhancing the circuit's anti-electromagnetic interference capability; in addition, by increasing the voltage values ​​of the first to third reference voltages in sequence, setting the third reference voltage value between the output voltage value of the first comparator when the capacitive touch button is not touched and the output voltage value of the first comparator when the capacitive touch button is touched by a finger, and setting the feedback capacitor between 1pF and 100pF, false triggering can be effectively prevented while effectively improving the capacitance increase detection range of the circuit, so that the capacitance increase detection range of the circuit can be as small as 1pF, but it does not solve the existing problem that as the touch scheme becomes more and more complex, more and more touch buttons are required, and a single IC can integrate dozens of buttons, and at the same time, the peripheral reference C x The capacitance requirement is generally less than 10nf, which puts higher requirements on the sensitivity of the touch button circuit. In the touch button circuit structure of the prior art solution, since all buttons are connected in parallel through switches to the touch circuit, the charge transfer circuit (capacitor charging and discharging) is shared, and the parasitic capacitance C of the button pin and the touch channel routing isL Very large. When the external noise interference is obvious, the capacitance value of the key changes little after the finger touches the key, C x The charge and discharge times change slightly, and there is a risk of being drowned in noise, and the occurrence of touch actions may not be effectively determined. For this reason, we propose a high-sensitivity touch button circuit. Summary of the invention

[0004] The object of the present invention is to provide a high-sensitivity touch key circuit to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a high-sensitivity touch key circuit, including a touch circuit and a charge transfer circuit,

[0006] The touch circuit includes a left channel key KL1 and a right channel key KR1. The left channel key KL1 includes a left channel key port parasitic capacitor C PL1 , left channel button finger touch capacitance C fL1 , a left channel key switch S1L1, and a key internal charging switch S2L1, wherein one end of the left channel key switch S1L1 is electrically connected to a left channel routing parasitic capacitor C LL , the key internal charging switch S2L1 is electrically connected to the main control chip, the four pins of the main control chip are electrically connected to transistors, the four groups of transistors are electrically connected in series and parallel, the two upper groups of transistors are electrically connected to the working mode selection signal CHA_SEL, and the two upper groups of transistors are also electrically connected to the left and right channel selection signal LRCH_SEL, the four groups of transistors are electrically connected to the charge transfer module key charging switch signal S2L, the charge transfer module key charging switch signal S2R, the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R, and the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R are electrically connected to the external reference capacitor discharge switch signal C x _DISCH and external charging capacitor C x The right channel button KR1 includes a right channel button port parasitic capacitance C PR1 , Right channel button finger touch capacitance C fR1 , right channel button switch S1R1, button internal charging switch S2R1;

[0007] The charge transfer circuit includes a sub-control chip, a switch S2 and a switch S3 are electrically connected to the sub-control chip, a switch S1 is electrically connected between the switch S2 and the switch S3, and a capacitor C is electrically connected to one side of the switch S2. p and capacitor C f, one side of the switch S3 is electrically connected to the capacitor C x and the external reference capacitor discharge switch signal C x _DISCH.

[0008] Preferably, the parasitic capacitance C of the left channel button port PL1 One side is electrically connected to the left channel key finger touch capacitor C fL1 , the left channel key switch S1L1 and the left channel key finger touch capacitance C fL1 The key internal charging switch S2L1 is electrically connected to the left channel key switch S1L1 and the left channel key finger touch capacitor C fL1 between.

[0009] Preferably, the parasitic capacitance C of the right channel button port PR1 One side is electrically connected to the right channel key finger touch capacitor C fR1 The right channel key switch S1R1 and the right channel key finger touch capacitance C fR1 The key internal charging switch S2R1 is electrically connected to the right channel key switch S1R1 and the right channel key finger touch capacitor C fR1 between.

[0010] Preferably, the parasitic capacitance C of the left channel button port PL1 And the left channel button finger touch capacitance C fL1 The parasitic capacitance C of the right channel button port is PR1 And the right channel button finger touch capacitance C fR1 Electrically grounded.

[0011] Preferably, the parasitic capacitance C of the left channel wiring LL , parasitic capacitance C of the right channel trace LR One side of the capacitor is electrically connected to a switch and a capacitor, and the capacitor is electrically grounded.

[0012] Preferably, the parasitic capacitance C of the left channel wiring LL and the parasitic capacitance C of the right channel trace LR One side is electrically grounded.

[0013] Preferably, the external reference capacitor discharge switch signal C x _DISCH and the external charging large capacitor C x One side is electrically grounded.

[0014] Preferably, an inverter is electrically connected between the working mode selection signal CHA_SEL and the transistor on one side.

[0015] Preferably, the capacitor C p , the capacitor C f and the capacitor C x One side is electrically grounded

[0016] Preferably, a capacitor C is electrically connected between the switch S1 and the switch S3. l , the capacitor C l One side is electrically grounded.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention adopts two working modes. The first is the normal working mode, which divides the touch buttons into two groups, the left and right groups, and reduces the parasitic capacitance of the single-side touch channel by physical means to improve the sensitivity of touch recognition. The second is the high-sensitivity working mode, which is used when the peripheral reference capacitance is small (<10nf) and the working environment interference is large. The key charging structure is distributed in the independent port structure of each key, and the key capacitance C p The charging is controlled by switch S2; the key charging switch signal (CHA_ENL) enables the PMOS driver tube in the corresponding PAD of the key to charge the key capacitor, and the key switch signal S1L1 / R1 is disconnected to eliminate the influence of the channel parasitic capacitance. Then the discharge switch signal (DISCH_ENL) enables the switch signal S1L1 / R1, the switch is closed, and the charge of the key capacitor is transferred to C x Capacitance transfer;

[0019] (2) A distributed charge transfer structure is proposed to eliminate the influence of parasitic capacitance when the number of keys is large and the peripheral reference capacitance is small, thereby achieving accurate judgment of touch actions under harsh working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a circuit diagram of the present invention;

[0021] Figure 2 A single key charge transfer circuit diagram of the present invention;

[0022] Figure 3 This is a working timing diagram of the touch circuit of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1-Figure 3 The present invention provides a technical solution: a high-sensitivity touch key circuit, including a touch circuit and a charge transfer circuit,

[0025] The touch circuit includes a left channel key KL1 and a right channel key KR1. The left channel key KL1 includes a left channel key port parasitic capacitor C PL1 , left channel button finger touch capacitance C fL1 , a left channel key switch S1L1, and a key internal charging switch S2L1, wherein one end of the left channel key switch S1L1 is electrically connected to a left channel routing parasitic capacitor C LL , the key internal charging switch S2L1 is electrically connected to the main control chip, the four pins of the main control chip are electrically connected to transistors, the four groups of transistors are electrically connected in series and parallel, the two upper groups of transistors are electrically connected to the working mode selection signal CHA_SEL, and the two upper groups of transistors are also electrically connected to the left and right channel selection signal LRCH_SEL, the four groups of transistors are electrically connected to the charge transfer module key charging switch signal S2L, the charge transfer module key charging switch signal S2R, the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R, and the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R are electrically connected to the external reference capacitor discharge switch signal C x _DISCH and external charging capacitor C x The right channel button KR1 includes a right channel button port parasitic capacitance C PR1 , Right channel button finger touch capacitance C fR1 , right channel button switch S1R1, button internal charging switch S2R1;

[0026] The charge transfer circuit includes a sub-control chip, a switch S2 and a switch S3 are electrically connected to the sub-control chip, a switch S1 is electrically connected between the switch S2 and the switch S3, and a capacitor C is electrically connected to one side of the switch S2. p and capacitor C f , one side of the switch S3 is electrically connected to the capacitor C x and the external reference capacitor discharge switch signal C x _DISCH.

[0027] In order to realize electrical protection for the left channel key KL1, in this embodiment, preferably, the parasitic capacitance C PL1 One side is electrically connected to the left channel key finger touch capacitor C fL1, the left channel key switch S1L1 and the left channel key finger touch capacitance C fL1 The key internal charging switch S2L1 is electrically connected to the left channel key switch S1L1 and the left channel key finger touch capacitor C fL1 between.

[0028] In order to realize electrical protection for the right channel key KR1, in this embodiment, preferably, the parasitic capacitance C PR1 One side is electrically connected to the right channel key finger touch capacitor C fR1 The right channel key switch S1R1 and the right channel key finger touch capacitance C fR1 The key internal charging switch S2R1 is electrically connected to the right channel key switch S1R1 and the right channel key finger touch capacitor C fR1 between.

[0029] In order to realize that the system can stably receive large key information and stably transmit it, in this embodiment, preferably, the parasitic capacitance C of the left channel key port PL1 And the left channel button finger touch capacitance C fL1 The parasitic capacitance C of the right channel button port is PR1 And the right channel button finger touch capacitance C fR1 Electrically grounded.

[0030] In order to enable the system to operate stably, in this embodiment, preferably, the parasitic capacitance C LL , parasitic capacitance C of the right channel trace LR One side of the capacitor is electrically connected to a switch and a capacitor, and the capacitor is electrically grounded.

[0031] In this embodiment, preferably, the parasitic capacitance C of the left channel wiring LL and the parasitic capacitance C of the right channel trace LR One side is electrically grounded.

[0032] In this embodiment, preferably, the external reference capacitor discharge switch signal C x _DISCH and the external charging large capacitor C x One side is electrically grounded.

[0033] In this embodiment, preferably, an inverter is electrically connected between the working mode selection signal CHA_SEL and the transistor on one side.

[0034] In this embodiment, preferably, the capacitor C p , the capacitor C f and the capacitor Cx One side is electrically grounded

[0035] In this embodiment, preferably, a capacitor C is electrically connected between the switch S1 and the switch S3. l , the capacitor C l One side is electrically grounded.

[0036] The working principle and use process of the present invention:

[0037] Normal working mode: used when the peripheral reference capacitance is large (>30nf) and the working environment interference is small. Divide the touch buttons into two groups, the parasitic capacitance of the single-side touch channel is reduced by physical means, and the sensitivity of touch recognition is improved.

[0038] The touch scan clock CTCK first turns on the charge transfer module key charging switch S2L and the charge transfer module key charging switch S2R to charge the parasitic capacitance of the TK pin, then turns off the charge transfer module key charging switch S2L and the charge transfer module key charging switch S2R, turns on the external reference capacitor charging switch S3L and the external reference capacitor charging switch S3R, and transfers the charge on the TK pin capacitor to the external charging large capacitor C x On, and so on, when V(C x ) After the voltage is greater than the reference voltage VREF, the comparator state flips, outputs a high level, the latch SR is reset, the scan clock CTCK input is shielded, the switch charge transfer module key charging switch S2L and the charge transfer module key charging switch S2R are turned off, the external reference capacitor charging switch S3L and the external reference capacitor charging switch S3R are turned on, and C x _DISCH signal becomes high level, external large capacitor C is charged x , the TK pin capacitor is discharged to 0V through the N1 tube. During this process, the left channel key switch S1L1 and the right channel key 1 switch S1R1 are always closed. So far, a key scanning process ends until the next pulse of CTC_STH starts the next scan.

[0039] High-sensitivity working mode: used when the peripheral reference capacitance is small (<10nf) and the working environment interference is large. The key charging structure is distributed in the independent port structure of each key, and the key capacitance C p Charging is controlled by switch S2.

[0040] The working mode selection signal CHA_ENL enables the PMOS driver tube in the corresponding PAD of the key to charge the key capacitor, and the left channel key switch S1L1 and the right channel key switch S1R1 are disconnected to eliminate the influence of channel parasitic capacitance. Then the discharge switch signal (DISCH_ENL) enables the left channel key switch S1L1 and the right channel key switch S1R1, the switch is closed, and the charge of the key capacitor is charged to the external large capacitor C x Compared with the normal working mode, the key capacitor is charged independently mainly through the key pin driver tube, eliminating the influence of channel parasitic capacitance when the key is charged, greatly improving the touch sensitivity, and the other working processes are the same as the normal mode.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-sensitivity touch button circuit, including a touch circuit and a charge transfer circuit, characterized in that: The touch circuit includes a left channel key KL1 and a right channel key KR1. The left channel key KL1 includes a left channel key port parasitic capacitance C PL1 , left channel button finger touch capacitance C fL1 , a left channel key switch S1L1, and a key internal charging switch S2L1, wherein one end of the left channel key switch S1L1 is electrically connected to a left channel routing parasitic capacitor C LL The key internal charging switch S2L1 is electrically connected to the main control chip, and the four pins of the main control chip are electrically connected to transistors respectively. The four groups of transistors are electrically connected in series and parallel respectively. The two groups of transistors on the upper side are electrically connected with the working mode selection signal CHA_SEL, and the two groups of transistors on the upper side are also electrically connected with the left and right channel selection signal LRCH_SEL. The four groups of transistors are electrically connected with the charge transfer module key charging switch signal S2L, the charge transfer module key charging switch signal S2R, the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R respectively, and the external reference capacitor charging switch signal S3L and the external reference capacitor charging switch signal S3R are electrically connected with the external reference capacitor discharge switch signal C x _DISCH and external charging capacitor C x The right channel button KR1 includes a right channel button port parasitic capacitance C PR1 , Right channel button finger touch capacitance C fR1 , right channel button switch S1R1, button internal charging switch S2R1; The charge transfer circuit includes a sub-control chip, a switch S2 and a switch S3 are electrically connected to the sub-control chip, a switch S1 is electrically connected between the switch S2 and the switch S3, and a capacitor C is electrically connected to one side of the switch S2. p and capacitor C f , one side of the switch S3 is electrically connected to the capacitor C x and the external reference capacitor discharge switch signal C x _DISCH; The parasitic capacitance C of the left channel button port PL1 One side is electrically connected to the left channel key finger touch capacitor C fL1 , the left channel key switch S1L1 and the left channel key finger touch capacitance C fL1 The key internal charging switch S2L1 is electrically connected to the left channel key switch S1L1 and the left channel key finger touch capacitor C fL1 between; The parasitic capacitance C of the right channel button port PR1 One side is electrically connected to the right channel key finger touch capacitor C fR1 The right channel key switch S1R1 and the right channel key finger touch capacitance C fR1 The key internal charging switch S2R1 is electrically connected to the right channel key switch S1R1 and the right channel key finger touch capacitor C fR1 between; The parasitic capacitance C of the left channel button port PL1 And the left channel button finger touch capacitance C fL1 The parasitic capacitance C of the right channel button port is PR1 And the right channel button finger touch capacitance C fR1 Uniform electrical grounding; The parasitic capacitance C of the left channel routing LL , Parasitic capacitance of right channel trace CLR One side of the device is electrically connected to a switch and a capacitor, respectively, and the capacitor is electrically grounded; The parasitic capacitance C of the left channel routing LL and the parasitic capacitance C of the right channel trace LR One side of the device is electrically grounded; The external reference capacitor discharge switch signal C x _DISCH and the external charging large capacitor C x One side of the device is electrically grounded; An inverter is electrically connected between the working mode selection signal CHA_SEL and the transistor on one side; The capacitor C p , the capacitor C f and the capacitor C x One side of the device is electrically grounded; A capacitor C is electrically connected between the switch S1 and the switch S3. l , the capacitor C l One side is electrically grounded.

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