1. A touch keyboard, comprising:

a key set;

a capacitance touch sensor coupled to the key set for generating an induction capacitance; and

a pressure sensing circuit coupled to the capacitive touch sensor for generating a pressure sensing value, the pressure sensing circuit comprising:

a converter coupled to an input pin for receiving a sensing signal provided from the input pin and outputting an analog voltage signal;

a cancellation circuit coupled between the converter and the input pin for generating a cancellation signal, so that the converter outputs the analog voltage signal according to the sensing signal added with the cancellation signal;

an analog-to-digital converter, coupled to the converter, for converting the analog voltage signal into a digital voltage signal; and

a digital signal processor coupled to the adc for generating the pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

2. A touch keyboard according to claim 1, wherein the content of the sensing signal is the sensing capacitance generated by the capacitive touch sensor, and the input pin is used to couple the pressure sensing circuit to an output of the capacitive touch sensor.

3. A touch keyboard according to claim 2, wherein said transducer is a capacitive voltage transducer and comprises:

an operational amplifier having an inverting input terminal coupled to a node between the input pin and the cancellation circuit, a non-inverting input terminal coupled to a ground voltage, and an output terminal coupled to the analog-to-digital converter; and

and the negative feedback circuit is coupled between the inverting input end of the operational amplifier and the output end of the operational amplifier, wherein the negative feedback circuit is composed of a first capacitor and a first switch which are mutually connected in parallel, and the first switch is controlled by a first control signal to determine the on or off state of the first switch.

4. A touch keyboard according to claim 3, wherein the pressure sensing circuit further comprises:

a second switch coupled between the input pin and the node and controlled by a second control signal to determine its own on or off state; and

a third switch coupled between the input pin and the ground voltage and controlled by the first control signal to determine its own on or off state;

the first control signal controls the first switch and the third switch to be in the conducting state for the same time, and the first control signal controls the first switch and the third switch to be in the conducting state for the time staggered with the time for the second control signal to control the second switch to be in the conducting state.

5. The touch keyboard of claim 4, wherein the cancellation circuit is a branch line coupled between the node and the ground voltage for reducing the sensing capacitance generated by the capacitive touch sensor such that the capacitive-to-voltage converter outputs the analog voltage signal according to the reduced sensing capacitance.

6. A touch keyboard as recited in claim 5, wherein said branch wiring comprises:

and a constant current source circuit, wherein when the second control signal controls the second switch to be in a conducting state, the constant current source circuit is used for attenuating the sensing capacitance generated by the capacitive touch sensor according to a preset parameter, so that the capacitance-to-voltage converter outputs the analog voltage signal according to the attenuated sensing capacitance.

7. A touch keyboard as recited in claim 2, wherein said cancellation circuit comprises:

a signal generator for generating the cancellation signal, wherein the polarity of the cancellation signal generated by the signal generator is opposite to the polarity of the sensing capacitance generated by the capacitive touch sensor; and

and the addition circuit is used for adding the induction capacitance generated by the capacitive touch sensor and the elimination signal and providing the induction capacitance added with the elimination signal to the converter.

8. A touch keyboard according to claim 7, wherein said transducer is a capacitive voltage transducer and comprises:

an operational amplifier having an inverting input terminal coupled to the input pin through the adder circuit, a non-inverting input terminal coupled to a reference voltage, and an output terminal coupled to the adc; and

and the negative feedback circuit is coupled between the inverting input end of the operational amplifier and the output end of the operational amplifier, wherein the negative feedback circuit is composed of a first capacitor and a first resistor which are mutually connected in parallel.

9. A touch keyboard, comprising:

a key set;

a capacitance touch sensor coupled to the key set for generating an induction capacitance; and

a pressure sensing circuit coupled to the capacitive touch sensor for generating a pressure sensing value, the pressure sensing circuit comprising:

a converter coupled to an input pin for receiving a sensing signal provided from the input pin and outputting an analog voltage signal;

an analog-to-digital converter, coupled to the converter, for converting the analog voltage signal into a digital voltage signal;

a cancellation circuit coupled between the converter and the adc for generating a cancellation signal, so that the adc outputs the digital voltage signal according to the analog voltage signal subtracted by the cancellation signal; and

a digital signal processor coupled to the adc for generating the pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

10. A touch keyboard according to claim 9, wherein the content of the sensing signal is the sensing capacitance generated by the capacitive touch sensor, and the input pin is used to couple the pressure sensing circuit to an output of the capacitive touch sensor.

11. A touch keyboard according to claim 10, wherein said transducer is a capacitive voltage transducer and comprises:

a first operational amplifier having an inverting input terminal coupled to the input pin, a non-inverting input terminal coupled to a ground voltage, and an output terminal coupled to the analog-to-digital converter; and

a first negative feedback circuit coupled between the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier, wherein the first negative feedback circuit is composed of a first capacitor and a first resistor connected in parallel.

12. A touch keyboard as recited in claim 11, wherein said cancellation circuit comprises:

a subtraction circuit coupled between the output terminal of the first operational amplifier and the analog-to-digital converter;

a second operational amplifier having an inverting input terminal coupled to an input terminal of the capacitive touch sensor, a non-inverting input terminal coupled to the ground voltage, and an output terminal coupled to the subtraction circuit;

a second negative feedback circuit coupled between the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier, wherein the second negative feedback circuit is composed of a second capacitor and a second resistor connected in parallel; and

and the reference capacitor is coupled between the inverting input end of the second operational amplifier and the input end of the capacitive touch sensor.

13. A touch keyboard according to claim 12, wherein the second operational amplifier, the second negative feedback circuit, the reference capacitor and the capacitor voltage converter are commonly disposed on a same chip substrate, and when a driving signal is inputted to the input terminal of the capacitive touch sensor, the second operational amplifier starts to output a reference voltage signal according to the reference capacitor, and the subtraction circuit is configured to subtract the analog voltage signal outputted by the capacitor voltage converter from the reference voltage signal outputted by the second operational amplifier and provide the subtracted result to the analog-to-digital converter.

14. A touch keyboard as recited in claim 10, wherein said cancellation circuit is integrated into said converter, and said converter is a capacitive voltage converter comprising:

an operational amplifier having an inverting input terminal coupled to the input pin, a non-inverting input terminal coupled to an input terminal of the capacitive touch sensor, and an output terminal coupled to the analog-to-digital converter; and

and the negative feedback circuit is coupled between the inverting input end of the operational amplifier and the output end of the operational amplifier, wherein the negative feedback circuit is composed of a first capacitor and a first resistor which are mutually connected in parallel.

15. A touch keyboard as recited in claim 14, wherein said capacitive voltage converter further comprises:

a positive feedback circuit coupled between the non-inverting input terminal of the operational amplifier and the output terminal of the operational amplifier, wherein the positive feedback circuit and the negative feedback circuit are formed by a second capacitor and a second resistor connected in parallel; and

a reference capacitor coupled between the inverting input of the operational amplifier and the input of the capacitive touch sensor.

16. A touch keyboard as recited in claim 10, wherein said cancellation circuit is integrated into said converter, and said converter is a capacitive voltage converter comprising:

an operational amplifier having an inverting input terminal coupled to the input pin, a non-inverting input terminal coupled to a signal generator, and an output terminal coupled to the analog-to-digital converter;

a negative feedback circuit coupled between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier, wherein the negative feedback circuit is composed of a first capacitor and a first resistor connected in parallel; and

a positive feedback circuit coupled between the non-inverting input terminal of the operational amplifier and the output terminal of the operational amplifier, wherein the positive feedback circuit and the negative feedback circuit are formed by a second capacitor and a second resistor connected in parallel.

17. A touch keyboard, comprising:

a key set;

a capacitance touch sensor coupled to the key set for generating an induction capacitance; and

a pressure sensing circuit coupled to the capacitive touch sensor for generating a pressure sensing value, the pressure sensing circuit comprising:

a converter coupled to an input pin for receiving a sensing signal provided from the input pin and outputting an analog voltage signal;

a suppression circuit, coupled between the converter and the input pin, for suppressing the sensing signal according to a predetermined parameter and providing the suppressed sensing signal to the converter, so that the converter outputs the analog voltage signal according to the suppressed sensing signal;

an analog-to-digital converter, coupled to the converter, for converting the analog voltage signal into a digital voltage signal; and

a digital signal processor coupled to the adc for generating the pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

18. A touch keyboard according to claim 17, wherein the content of the sensing signal is the sensing capacitance generated by the capacitive touch sensor, and the input pin is used to couple the pressure sensing circuit to an output of the capacitive touch sensor.

19. A touch keyboard according to claim 18, wherein said transducer is a capacitive voltage transducer and comprises:

a first operational amplifier having an inverting input terminal coupled to the input pin through the suppression circuit, a non-inverting input terminal coupled to a reference voltage, and an output terminal coupled to the analog-to-digital converter; and

and the negative feedback circuit is coupled between the inverting input end of the first operational amplifier and the output end of the first operational amplifier, wherein the negative feedback circuit is composed of a first capacitor and a first resistor which are mutually connected in parallel.

20. The touch keyboard of claim 19, wherein the suppression circuit is an impedance element coupled between the inverting input terminal and the input pin of the first operational amplifier, wherein the impedance element is configured to suppress the induced capacitance generated by the capacitive touch sensor according to an impedance value of the impedance element as the predetermined parameter, such that the capacitive voltage converter outputs the analog voltage signal according to the suppressed induced capacitance.

21. A touch keyboard according to claim 20, wherein said impedance element is formed by at least one passive element.

22. The touch keyboard of claim 19, wherein the suppression circuit is a voltage divider circuit, and the voltage divider circuit comprises a second resistor and a third resistor, wherein the second resistor is coupled between the inverting input terminal and the input pin of the first operational amplifier, a first terminal of the third resistor is coupled to a node between the second resistor and the input pin, and a second terminal of the third resistor is coupled to the reference voltage.

23. A touch keyboard according to claim 19, wherein said inhibit circuit comprises, when said reference voltage is a ground voltage:

a second resistor coupled between the inverting input terminal and the input pin of the first operational amplifier;

a second operational amplifier having a non-inverting input coupled to the ground voltage and an inverting input coupled to an output of the second operational amplifier; and

a third resistor having a first end coupled to a node between the input pin and the second resistor, and a second end coupled to the output end of the second operational amplifier.

24. A touch keyboard, comprising:

a key set;

a capacitance touch sensor coupled to the key set for generating an induction capacitance; and

a pressure sensing circuit coupled to the capacitive touch sensor for generating a pressure sensing value, the pressure sensing circuit comprising:

a converter coupled to an input pin for receiving a capacitance sensing signal provided from the input pin and outputting a circuit signal corresponding to a pressure value sensed by the capacitance sensing signal; and

and the elimination circuit is coupled between the converter and the input pin and used for generating an elimination signal, so that the converter outputs the circuit signal according to the capacitance sensing signal added with the elimination signal.

25. A touch keyboard according to claim 24, wherein said circuit signal is a voltage signal, and a voltage value of said voltage signal is proportional to said value of said pressure sensed by said capacitive sensing signal.

26. The touch keyboard of claim 25, wherein the voltage signal is an analog voltage signal, and the converter is further coupled to an analog-to-digital converter for converting the analog voltage signal to a digital voltage signal.

27. The touch keyboard of claim 26, wherein the pressure sensing circuit further comprises a digital signal processor coupled to the analog-to-digital converter for generating the pressure sensing value corresponding to the capacitive sensing signal based on the digital voltage signal.

Background

Compared with the conventional keyboard, the touch keyboard integrates the touch panel into the keyboard, so that the keyboard can have a touch function at the same time, for example, a user can control cursor movement by sliding a finger on the surface of the keyboard. In addition, most touch panels in the market currently adopt capacitive touch sensors, and for a touch keyboard comprising the capacitive touch sensors, the principle is to use different induced capacitances generated by the capacitive touch sensors due to the pressing of a user and the touching of a key set to judge whether the user presses or touches the key set.

However, the strength of the induced capacitance generated by the capacitive Touch sensor when the user presses the key set is much greater than that generated by the user touching the key set, so that when two applications, i.e., pressing the key and touching the Keyboard (TOK), can exist simultaneously, the conventional capacitive voltage converter is prone to Overflow, and the induced capacitance cannot be correctly converted into a corresponding voltage value. That is, the touch keypad needs a large detection range to be able to detect the pressed key and the touch keypad at the same time, and means that the detection range is very important to the sensitivity of the touch keypad. Therefore, there is a need in the art for a touch keyboard that prevents the capacitive-to-voltage converter from overflowing due to receiving excessive sensing capacitance.

Disclosure of Invention

In view of this, an embodiment of the present invention provides a touch keyboard, which includes a key set, a capacitive touch sensor, and a pressure sensing circuit. The capacitive touch sensor is coupled to the key set and used for generating an induction capacitance. The pressure sensing circuit is coupled to the capacitive touch sensor, is used for generating a pressure sensing value, and comprises a converter, a cancellation circuit, an analog-to-digital converter and a digital signal processor. The converter is coupled to the input pin and is used for receiving the sensing signal provided by the input pin and outputting an analog voltage signal. The cancellation circuit is coupled between the converter and the input pin and used for generating a cancellation signal, so that the converter outputs an analog voltage signal according to the sensing signal added with the cancellation signal. The analog-to-digital converter is coupled to the converter and is used for converting the analog voltage signal into a digital voltage signal. The digital signal processor is coupled to the analog-to-digital converter and used for generating a pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

The embodiment of the invention also provides a touch keyboard, which comprises a key group, a capacitive touch sensor and a pressure sensing circuit. The capacitive touch sensor is coupled to the key set and used for generating an induction capacitance. The pressure sensing circuit is coupled to the capacitive touch sensor, is used for generating a pressure sensing value, and comprises a converter, an analog-digital converter, a cancellation circuit and a digital signal processor. The converter is coupled to the input pin and is used for receiving the sensing signal provided by the input pin and outputting an analog voltage signal. The analog-to-digital converter is coupled to the converter and is used for converting the analog voltage signal into a digital voltage signal. The cancellation circuit is coupled between the converter and the analog-to-digital converter and used for generating a cancellation signal, so that the analog-to-digital converter outputs a digital voltage signal according to the analog voltage signal obtained by subtracting the cancellation signal. The digital signal processor is coupled to the analog-to-digital converter and used for generating a pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

The embodiment of the invention also provides a touch keyboard, which comprises a key group, a capacitive touch sensor and a pressure sensing circuit. The capacitive touch sensor is coupled to the key set and used for generating an induction capacitance. The pressure sensing circuit is coupled to the capacitive touch sensor, is used for generating a pressure sensing value, and comprises a converter, a suppression circuit, an analog-to-digital converter and a digital signal processor. The converter is coupled to the input pin and is used for receiving the sensing signal provided by the input pin and outputting an analog voltage signal. The suppression circuit is coupled between the converter and the input pin and used for suppressing the sensing signal according to a preset parameter and then providing the suppressed sensing signal to the converter, so that the converter outputs an analog voltage signal according to the suppressed sensing signal. The analog-to-digital converter is coupled to the converter and is used for converting the analog voltage signal into a digital voltage signal. The digital signal processor is coupled to the analog-to-digital converter and used for generating a pressure sensing value corresponding to the sensing signal according to the digital voltage signal.

Preferably, the converters are all capacitance-to-voltage converters, and the content of the sensing signal is an induced capacitance generated by the capacitive touch sensor. In addition, the input pin is used for coupling the pressure sensing circuit to the output end of the capacitive touch sensor.

In addition, the embodiment of the invention further provides a touch keyboard, which comprises a key group, a capacitive touch sensor and a pressure sensing circuit. The capacitive touch sensor is coupled to the key set and used for generating an induction capacitance. The pressure sensing circuit is coupled to the capacitive touch sensor, generates a pressure sensing value, and includes a converter and a cancellation circuit. The converter is coupled to the input pin, and is used for receiving the capacitance sensing signal provided by the input pin and outputting a circuit signal corresponding to a pressure value sensed by the capacitance sensing signal. The cancellation circuit is coupled between the converter and the input pin and used for generating a cancellation signal, so that the converter outputs a circuit signal according to the capacitance sensing signal added with the cancellation signal.

Preferably, the circuit signal is a voltage signal, and a voltage value of the voltage signal is proportional to a pressure value sensed by the capacitance sensing signal. In addition, the voltage signal is an analog voltage signal, and the converter can be coupled to an analog-to-digital converter for converting the analog voltage signal into a digital voltage signal.

For a better understanding of the features and technical content of the present invention, reference should be made to the following detailed description of the invention and accompanying drawings, which are provided for purposes of illustration and description only and are not intended to limit the invention.

Drawings

Fig. 1 is a functional block diagram of a touch keyboard according to a first embodiment of the present invention.

Fig. 2 is a circuit schematic diagram of the converter and cancellation circuit of fig. 1 under a first preferred embodiment.

Fig. 3 is a circuit schematic diagram of the converter and cancellation circuit of fig. 1 under a second preferred embodiment.

Fig. 4 is a functional block diagram of a touch keyboard according to a second embodiment of the present invention.

Fig. 5 is a circuit schematic diagram of the converter and cancellation circuit of fig. 4 under a first preferred embodiment.

Fig. 6 is a circuit schematic diagram of the converter and cancellation circuit of fig. 4 under a second preferred embodiment.

Fig. 7 is a circuit schematic diagram of the converter and cancellation circuit of fig. 4 in a third preferred embodiment.

Fig. 8 is a functional block diagram of a touch keyboard according to a third embodiment of the present invention.

Fig. 9 is a circuit schematic diagram of the converter and suppression circuit of fig. 8 under a first preferred embodiment.

Fig. 10 is a circuit schematic of the converter and suppression circuit of fig. 8 under a second preferred embodiment.

Fig. 11 is a circuit schematic diagram of the converter and suppression circuit of fig. 8 in a third preferred embodiment.

Detailed Description

The following is a description of embodiments of the present invention with reference to specific embodiments, and those skilled in the art will understand the advantages and effects of the present invention from the contents provided in the present specification. The invention is capable of other and different embodiments and its several details are capable of modification and various other changes, which can be made in various details within the specification and without departing from the spirit and scope of the invention. The drawings of the present invention are for illustrative purposes only and are not intended to be drawn to scale. The following embodiments will further explain the related art of the present invention in detail, but the contents are not provided to limit the scope of the present invention.

It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are used primarily to distinguish one element from another element or from one signal to another signal. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.

Referring to fig. 1, fig. 1 is a functional block diagram of a touch keyboard according to a first embodiment of the present invention. The touch keyboard 1 comprises a key group 10, a capacitive touch sensor TK1 and a pressure sensing circuit 12. The capacitive touch sensor TK1 is coupled to the keypad 10 for generating sensing capacitance. Please note that the present invention is not limited to the specific implementation of the key set 10 and the capacitive touch sensor TK1, and for convenience of the following description, the capacitive touch sensor TK1 of the present invention only adopts the example with the number of 1, but it is not used to limit the present invention, and in summary, since the operation principles of the key set 10 and the capacitive touch sensor TK1 are already existing in the art, the details of the key set 10 and the capacitive touch sensor TK1 will not be repeated.

In addition, the pressure sensing circuit 12 is coupled to the capacitive touch sensor TK1 for generating a pressure sensing value Pv, and includes a converter 120, a cancellation circuit 122, an analog-to-digital converter 124, and a digital signal processor 126. The converter 120 is coupled to the input pin P1, and is configured to receive the sensing signal S1 provided from the input pin P1 and output an analog voltage signal VS 1. The cancellation circuit 122 is coupled between the converter 120 and the input pin P1 for generating a cancellation signal S2, such that the converter 120 outputs an analog voltage signal VS1 according to the sensing signal S1 added with the cancellation signal S2. The analog-to-digital converter 124 is coupled to the converter 120 for converting the analog voltage signal VS1 into a digital voltage signal VS 2. The digital signal processor 126 is coupled to the analog-to-digital converter 124 and is used for generating a pressure sensing value Pv corresponding to the sensing signal S1 according to the digital voltage signal VS 2.

However, since the operation principles of the analog-to-digital converter 124 and the digital signal processor 126 are also well known to those skilled in the art, the details of the analog-to-digital converter 124 and the digital signal processor 126 are not repeated herein. As will be appreciated by those skilled in the art in light of the foregoing, the sensing signal S1 is the induced capacitance generated by the capacitive touch sensor TK1, and the input pin P1 is used to couple the pressure sensing circuit 12 to the output OUT of the capacitive touch sensor TK 1. Next, the implementation of the converter 120 and the cancellation circuit 122 will be further described below.

Referring to fig. 2, fig. 2 is a circuit diagram of the converter 120 and the cancellation circuit 122 of fig. 1 according to a first preferred embodiment. As shown in fig. 2, the converter 120 may be, for example, a capacitance-to-voltage converter 220, and includes an operational amplifier 2201 and a negative feedback circuit 2202. The Inverting Input (Inverting Input) of the operational amplifier 2201 is coupled to the node a between the Input pin P1 and the cancellation circuit 122, and the Non-Inverting Input (Non-Inverting Input) of the operational amplifier 2201 is coupled to the ground voltage GND, and the output of the operational amplifier 2201 is coupled to the adc 124. In addition, the negative feedback circuit 2202 is coupled between the inverting input terminal of the operational amplifier 2201 and the output terminal of the operational amplifier 2201, and the negative feedback circuit 2202 is formed by the first capacitor Cf and the first switch SW1 connected in parallel. In the present embodiment, the first switch SW1 is controlled by the first control signal TS1 to determine its own on or off state.

Since the operation principle of the capacitor-to-voltage converter 220 is well known to those skilled in the art, details of the operational amplifier 2201 and the negative feedback circuit 2202 will not be described herein. Conversely, as mentioned above, when the sensing capacitance generated by the capacitive touch sensor TK1 is too large, the capacitive voltage converter 220 is prone to overflow, and the sensing capacitance cannot be correctly converted into the corresponding voltage value. That is, the capacitance-to-voltage converter 220 will not effectively output the analog voltage signal VS1 corresponding to the sensing capacitance. Therefore, the technical core of the first embodiment of the present invention is that the elimination circuit 122 additionally disposed between the input pin P1 and the capacitance voltage converter 220 is used to attenuate the sensing capacitance generated by the capacitive touch sensor TK1, i.e., the sensing signal S1, so as to prevent the capacitance voltage converter 220 in the touch keyboard 1 from overflowing due to receiving an excessive sensing capacitance, and enable the capacitance voltage converter 220 to effectively output the analog voltage signal VS1 corresponding to the attenuated sensing capacitance.

It should be noted that the present invention is not limited to the specific implementation of the sensing capacity, i.e. the sensing signal S1, for attenuation, and those skilled in the art should be able to design the sensing capacity according to the actual requirement or application. The above-mentioned "attenuating the induced capacitance" may mean that the attenuation effect is achieved by a quantitative method or a non-quantitative method, but the present invention is not limited thereto. In summary, based on the above teachings and the prior art, it should be understood that the capacitive-to-voltage converter 220 in fig. 2 can also be regarded as a Discrete (Discrete) type circuit design. Accordingly, the pressure sensing circuit 12 of FIG. 2 may also include a second switch SW2 and a third switch SW 3.

In the present embodiment, the second switch SW2 is coupled between the input pin P1 and the node a and controlled by the second control signal TS2 to determine its own on or off state. In addition, the third switch SW3 is coupled between the input pin P1 and the ground voltage GND, and is controlled by the first control signal TS1 to determine its on or off state. That is, the first control signal TS1 controls the first and third switches SW1 and SW3 to be in the same on state for the same time, and the first control signal TS1 controls the first and third switches SW1 and SW3 to be in the on state for the same time, so the time for the second control signal TS2 to control the second switch SW2 to be in the on state is staggered with each other, as shown in fig. 2, there is a partial operation timing sequence for the first control signal TS1 and the second control signal TS2, and therefore, the description thereof is not repeated herein.

However, to further illustrate how the sensing capacitance, i.e., the sensing signal S1, is attenuated, the present invention provides the following specific implementation. As shown in fig. 2, the canceling circuit 122 may be, for example, a branch 222, coupled between the node a and the ground voltage GND, for reducing the sensing capacitance generated by the capacitive touch sensor TK1, such that the capacitive-voltage converter 220 outputs the analog voltage signal VS1 according to the reduced sensing capacitance. In the present embodiment, the degree of the capacitance attenuation of the branch connection 222 may be determined by a predetermined parameter or based on the current operating environment (e.g., operating temperature, average sensing capacitance, etc.) of the pressure sensing circuit 1, but the invention is not limited thereto.

In addition, the branch wiring 222 may further include a constant current source circuit 222a if it is considered that the attenuation effect is achieved by way of quantification. When the second control signal TS2 controls the second switch SW2 to be in a conducting state, the constant current source circuit 222a is used for attenuating the sensing capacitance generated by the capacitive touch sensor TK1 according to a predetermined parameter, so that the capacitive-voltage converter 220 outputs the analog voltage signal VS1 according to the attenuated sensing capacitance. It should be noted that, since the operation principle of the constant current source circuit 222a is already known by those skilled in the art, details of the constant current source circuit 222a will not be described herein, and the above-mentioned "preset parameter" may be the constant current value I provided by the constant current source circuit 222 a. Therefore, the larger the constant current value I, the larger the attenuation degree of the induced capacitance, but the present invention is not limited to the specific implementation of the constant current value I.

It can be seen that, in the touch keypad 1 according to the first embodiment of the present invention, not only the constant current source circuit 222a is utilized to quantitatively attenuate the sensing capacitance generated by the capacitive touch sensor TK1, but also the time difference between the first switch SW1, the second switch SW2 and the third switch SW3 can be controlled in an interleaving manner, so as to avoid the abrupt variation of the first capacitor Cf in the capacitor-voltage converter 220, and enable the voltage converter 220 to output a more stable analog voltage signal VS 1. It should be noted that the implementation of the constant current source circuit 222a is only an example, and is not intended to limit the present invention. In addition, the capacitor-voltage converter 220 may be a Continuous (Continuous) type circuit design. Therefore, referring to fig. 3, fig. 3 is a circuit diagram of the converter 120 and the cancellation circuit 122 of fig. 1 according to a second preferred embodiment.

Compared to the capacitive voltage converter 220 of fig. 2, the capacitive voltage converter 320 of fig. 3 includes an operational amplifier 3201 and a negative feedback circuit 3202. The inverting input terminal of the operational amplifier 3201 is coupled to the input pin P1 through a summing circuit 3224, and the non-inverting input terminal of the operational amplifier 3201 is coupled to a reference voltage Vref, and the output terminal of the operational amplifier 3201 is coupled to the analog-to-digital converter 124. In addition, the negative feedback circuit 3202 is coupled between the inverting input terminal of the operational amplifier 3201 and the output terminal of the operational amplifier 3201, and the negative feedback circuit 3202 is formed by a first capacitor Cf and a first resistor Rf connected in parallel. Since the operation principle of the capacitor-to-voltage converter 320 is well known to those skilled in the art, details of the operational amplifier 3201 and the negative feedback circuit 3202 will not be described.

Similarly, for further explanation on how to attenuate the sensing capacitance, i.e. the sensing signal S1, the present invention provides another specific implementation. As shown in fig. 3, the cancellation circuit 122 may include a signal generator 3222 and an addition circuit 3224. The signal generator 3222 is configured to generate the cancellation signal S2, and a polarity of the cancellation signal S2 generated by the signal generator 3222 is opposite to a polarity of the sensing capacitance generated by the capacitive touch sensor TK1, i.e., the sensing signal S1. In addition, the adding circuit 3224 is configured to add the sensing capacitance generated by the capacitive touch sensor TK1 and the cancellation signal S2 generated by the signal generator 3222, and then provide the sensing capacitance added with the cancellation signal S2 to the capacitance-voltage converter 320. It should be noted that the above-mentioned implementation of the adding circuit 3224 is also only an example, and is not intended to limit the present invention.

For example, in other embodiments, when the polarity of the cancellation signal S2 generated by the signal generator 3222 is the same as the polarity of the sensing capacitance generated by the capacitive touch sensor TK1, the adding circuit 3224 may be replaced by a subtracting circuit (not shown in fig. 3). It can be seen that the subtraction circuit is used to subtract the sensing capacitance generated by the capacitive touch sensor TK1 from the cancellation signal S2 generated by the signal generator 3222, and then provide the sensing capacitance subtracted by the cancellation signal S2 to the capacitance-to-voltage converter 320. In other words, the operation manner, such as addition or subtraction, adopted by the cancellation circuit 122 for the attenuation of the sensing capacitance may be determined by the polarity of the cancellation signal S2 generated by the signal generator 3222 or according to the operation requirement of the current pressure sensing circuit 12, but the invention is not limited thereto.

That is, the touch keyboard 1 according to the second embodiment of the present invention can utilize the cancellation signal S2 generated by the signal generator 3222 to weaken the sensing capacitance generated by the capacitive touch sensor TK1, so as to prevent the capacitive voltage converter 320 from overflowing due to receiving an excessive sensing capacitance, and enable the capacitive voltage converter 320 to output the analog voltage signal VS1 corresponding to the attenuated sensing capacitance. In practice, the signal generator 3222 may be, for example, a digital-to-analog converter, but the invention is not limited thereto, and the magnitude of the cancellation signal S2 may be programmed by the signal generator 3222 according to the magnitude of the induced capacitance generated by the capacitive touch sensor TK 1. In summary, the present invention is not limited to the specific implementation of the sensing capacitance decay.

Likewise, if it is considered that the attenuation effect is achieved by quantification, in other embodiments, the magnitude of the cancellation signal S2 generated by the signal generator 3222 may be the same as the magnitude of the induced capacitance generated by the capacitive touch sensor TK1 when it is not pressed. Thus, the touch keyboard 1 according to the second embodiment of the present invention not only can completely cancel the induced capacitance generated by the capacitive touch sensor TK1 when not pressed by the cancellation signal S2 generated by the signal generator 3222, but also can quantitatively attenuate the induced capacitance generated by the capacitive touch sensor TK1 when pressed by the cancellation signal S2, so that the capacitive voltage converter 320 does not overflow due to receiving an excessive induced capacitance.

It can be seen that, in both the touch keyboard 1 of fig. 2 and 3, before the sensing capacitance generated by the capacitive touch sensor TK1, i.e. the sensing signal S1, is inputted to the converter 120, i.e. the capacitance-to-voltage converters 220 and 320, the sensing capacitance is attenuated by the cancellation circuit 122, so as to prevent the converter 120 from overflowing due to receiving an excessive sensing capacitance, and the converter 120 can effectively output the analog voltage signal VS1 corresponding to the attenuated sensing capacitance. However, if the probability of the converter 120 overflowing is not considered, in other embodiments, the cancellation circuit 122 may be modified to start to attenuate the analog voltage signal VS1 after the converter 120 outputs the analog voltage signal VS1 according to the induced capacitance generated by the capacitive touch sensor TK1, so that the adc 124 outputs the digital voltage signal VS2 according to the attenuated analog voltage signal VS 1. Therefore, referring to fig. 4, fig. 4 is a functional block diagram of a touch keyboard 4 according to a second embodiment of the present invention, and components in fig. 4 that are the same as or similar to those in fig. 1 are denoted by the same or similar symbols, so that the details thereof are not described herein again.

In brief, compared to the cancellation circuit 122 of fig. 1, the cancellation circuit 422 of fig. 4 is coupled between the converter 120 and the adc 124 for generating the cancellation signal S3, so that the adc 124 outputs the digital voltage signal VS2 according to the analog voltage signal VS1 obtained by subtracting the cancellation signal S3. Referring to fig. 5, fig. 5 is a circuit diagram of the converter 120 and the cancellation circuit 422 of fig. 4 according to a first preferred embodiment.

As shown in fig. 5, the converter 120 may be, for example, a capacitance-to-voltage converter 520, and includes an operational amplifier 5201 and a negative feedback circuit 5202. The inverting input terminal of the operational amplifier 5201 is coupled to the input pin P1, the non-inverting input terminal of the operational amplifier 5201 is coupled to the ground voltage GND, and the output terminal of the operational amplifier 5201 is coupled to the adc 124 through the subtraction circuit 4222. In addition, the negative feedback circuit 5202 is coupled between the inverting input terminal of the operational amplifier 5201 and the output terminal of the operational amplifier 5201. The negative feedback circuit 52020 is composed of a first capacitor Cf and a first resistor Rf connected in parallel to each other. Since the operation principle of the capacitor-to-voltage converter 520 is also known to those skilled in the art, details of the operational amplifier 5201 and the negative feedback circuit 5202 will not be described herein. Further, the cancellation circuit 422 of fig. 5 may include a subtraction circuit 4222, an operational amplifier 4224, a negative feedback circuit 4226, and a reference capacitor Cref.

The subtracting circuit 4222 is coupled between the output terminal of the operational amplifier 5201 and the analog-to-digital converter 124. An inverting input terminal of the operational amplifier 4224 is coupled to the input terminal IN of the capacitive touch sensor TK1, a non-inverting input terminal of the operational amplifier 4224 is coupled to the ground voltage GND, and an output terminal of the operational amplifier 4224 is coupled to the subtraction circuit 4222. The negative feedback circuit 4226 is coupled between the inverting input terminal of the operational amplifier 4224 and the output terminal of the operational amplifier 4224, and the negative feedback circuit 4226 is composed of a capacitor C1 and a resistor R1 connected in parallel. The reference capacitor Cref is coupled between the inverting input terminal of the operational amplifier 4224 and the input terminal IN of the capacitive touch sensor TK 1.

It should be understood that the operational amplifier 5201 and the negative feedback circuit 4226 can be regarded as the capacitor voltage converter 520 in the other branch. Therefore, the above-mentioned "capacitor C1 and resistor R1" may refer to the same capacitor and resistor as the first capacitor Cf and the first resistor Rf, respectively, but the present invention is not limited thereto, and in short, the present invention is not limited to the specific implementation manner of the capacitor-to-voltage converter 520 in the other branch line, and those skilled in the art should be able to design the operational amplifier 5201 and the negative feedback circuit 4226 according to actual requirements or applications.

As can be appreciated by those skilled IN the art, the operational amplifier 4224, the negative feedback circuit 4226, the reference capacitor Cref and the capacitor voltage converter 520 may be commonly disposed on the same chip substrate, and when a driving signal (not shown IN fig. 5) is inputted to the input terminal IN of the capacitive touch sensor TK1, even if the capacitive touch sensor TK1 starts sensing, the cancellation circuit 422 will enable the operational amplifier 4224 to start outputting a reference voltage signal VSf, i.e., the cancellation signal S3 IN fig. 4, according to the reference capacitor Cref. The subtraction circuit 4222 is used to subtract the analog voltage signal VS1 output by the capacitance-voltage converter 520 from the reference voltage signal VSf output by the operational amplifier 4224, and then provide the subtracted result to the analog-to-digital converter 124.

That is, the adc 124 outputs a digital voltage signal VS2 according to the attenuated analog voltage signal VS 1. The above-mentioned "subtracted result" may refer to a zero result or a non-zero result, but the present invention is not limited thereto. Therefore, the touch keypad 4 of fig. 5 can be programmed to design the reference capacitance Cref according to the induced capacitance generated by the capacitive touch sensor TK1, so that the operational amplifier 4224 can output a reference voltage signal VSf greater than, less than, or even equal to the analog voltage signal VS1 according to the reference capacitance Cref.

On the other hand, if it is considered that the attenuation effect is achieved by quantification, in other embodiments, the magnitude of the reference capacitance Cref may be preset to be equal to the magnitude of the induced capacitance generated by the capacitive touch sensor TK1 when not being pressed. Thus, when the capacitive touch sensor TK1 is not pressed and a driving signal is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keypad 4 of fig. 5 can completely cancel the analog voltage signal VS1 outputted by the capacitive voltage converter 520 by using the reference voltage signal VSf outputted by the operational amplifier 4224, so that the analog-to-digital converter 124 will only receive an analog voltage signal VS1 of zero.

Similarly, when the capacitive touch sensor TK1 is pressed, i.e. the sensing capacitance is larger than the reference capacitance Cref, and the driving signal is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keypad 4 of fig. 5 may further quantitatively subtract the analog voltage signal VS1 outputted by the capacitive voltage converter 520 by using the reference voltage signal VSf outputted by the operational amplifier 4224, so that the analog-to-digital converter 124 outputs the corresponding digital voltage signal VS2 according to the attenuated analog voltage signal VS 1. It should be noted that the above-mentioned specific implementation of the reference capacitor Cref is only an example, and it is not intended to limit the present invention, and those skilled in the art should be able to design the size of the reference capacitor Cref according to actual requirements or applications.

Referring to fig. 6, fig. 6 is a circuit diagram of the converter 120 and the cancellation circuit 422 of fig. 4 according to a second preferred embodiment. Compared to the cancellation circuit 422 of fig. 5, the cancellation circuit of fig. 6 is directly integrated into the converter 120, i.e., the capacitor-to-voltage converter 620. Therefore, as shown in fig. 6, the capacitance-to-voltage converter 620 includes an operational amplifier 6201, a negative feedback circuit 6202, a positive feedback circuit 6203, and a reference capacitance Cref. The inverting input terminal of the operational amplifier 6201 is coupled to the input pin P1, and the non-inverting input terminal of the operational amplifier 6201 is coupled to the input terminal IN of the capacitive touch sensor TK1 through the reference capacitor Cref, and is coupled to the output terminal of the operational amplifier 6201 and the analog-to-digital converter 124.

The negative feedback circuit 6202 is coupled between the inverting input terminal of the operational amplifier 6201 and the output terminal of the operational amplifier 6201, the negative feedback circuit 6202 is formed by a first capacitor Cf and a first resistor Rf connected in parallel, the positive feedback circuit 6203 is coupled between the non-inverting input terminal of the operational amplifier 6201 and the output terminal of the operational amplifier 6201, and the positive feedback circuit 6203 is formed by a capacitor C1 and a resistor R1 connected in parallel. Since the operation principle of the capacitor-to-voltage converter 620 is well known to those skilled in the art, details of the operational amplifier 6201, the negative feedback circuit 6202, and the positive feedback circuit 6203 are not repeated. It should be understood that the touch keypad 4 of fig. 6 can also be programmed to design the size of the reference capacitor Cref according to the induced capacitance generated by the capacitive touch sensor TK1, so that the capacitance-voltage converter 620 can output an attenuated analog voltage signal VS1 to the analog-to-digital converter 124 according to the reference capacitor Cref.

Similarly, if it is considered that the attenuation effect is achieved quantitatively, in other embodiments, the magnitude of the reference capacitance Cref may be preset to be equal to the magnitude of the induced capacitance generated by the capacitive touch sensor TK1 when not being pressed. Thus, when the capacitive touch sensor TK1 is not pressed and a driving signal (not shown IN fig. 6) is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keypad 4 of fig. 6 can output an analog voltage signal VS1 of zero by using the capacitive voltage converter 620. Similarly, when the capacitive touch sensor TK1 is pressed, i.e. the sensing capacitance is larger than the reference capacitance Cref, and the driving signal is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keypad 4 of fig. 6 can further output the attenuated analog voltage signal VS1 by using the capacitive voltage converter 620, so that the analog-to-digital converter 124 outputs the corresponding digital voltage signal VS2 according to the attenuated analog voltage signal VS 1.

Referring to fig. 7, fig. 7 is a circuit diagram of the converter 120 and the cancellation circuit 422 of fig. 4 in a third preferred embodiment, and components in fig. 7 that are the same as those in fig. 6 are denoted by the same symbols, so that details thereof will not be described herein. As shown in fig. 7, the cancellation circuit of fig. 7 is also directly integrated into the converter 120, i.e., the capacitance-to-voltage converter 720, but compared to the capacitance-to-voltage converter 620 of fig. 6, the capacitance-to-voltage converter 720 of fig. 7 utilizes the non-inverting input terminal of the operational amplifier 6201 to directly couple to a signal generator 7204. That is, the content of the reference signal RS generated by the signal generator 7204 is represented by the reference capacitance Cref of fig. 6.

Similarly, in other embodiments, the magnitude of the reference signal RS generated by the signal generator 7204 can be preset to be equal to the magnitude of the induced capacitance generated by the capacitive touch sensor TK1 when the capacitive touch sensor TK1 is not pressed, if it is considered that the attenuation effect is achieved by way of quantification. Thus, when the capacitive touch sensor TK1 is not pressed and a driving signal (not shown IN fig. 7) is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keyboard 4 of fig. 7 can output a zero analog voltage signal VS1 by using the capacitive voltage converter 720, and when the capacitive touch sensor TK1 is pressed, i.e., the sensing capacitance is larger than the reference signal RS, and the driving signal is inputted to the input terminal IN of the capacitive touch sensor TK1, the touch keyboard 4 of fig. 7 can further output an attenuated analog voltage signal VS1 by using the capacitive voltage converter 720, so that the analog-to-digital converter 14 outputs a corresponding digital voltage signal VS2 according to the attenuated analog voltage signal VS 1.

In practice, the signal generator 7204 may be a digital-to-analog converter, for example, but the invention is not limited thereto. In summary, compared to the touch keyboard 1 of fig. 1 to 3, the touch keyboard 4 of fig. 4 to 7 is modified to attenuate the analog voltage signal VS1 by the cancellation circuit 422 or the capacitive voltage converters 620, 720 before the analog voltage signal VS1 is inputted to the analog-to-digital converter 124, so that the analog-to-digital converter 124 outputs the digital voltage signal VS2 according to the attenuated analog voltage signal VS 1. Since the details are as described above, further description is omitted here.

On the other hand, as mentioned above, the present invention does not limit the specific implementation manner when the sensing capacitance is attenuated, so please refer to fig. 8, fig. 8 is a functional block diagram of a touch keyboard according to a third embodiment of the present invention, and the same components in fig. 8 as those in fig. 1 are denoted by the same symbols, so that the details thereof will not be described herein. As shown in fig. 8, the pressure sensing circuit 82 of the touch keypad 8 of fig. 8 mainly includes a suppression circuit 822 in addition to the converter 120, the analog-to-digital converter 124, and the digital signal processor 126, as compared to the pressure sensing circuit 12 of the touch keypad 1 of fig. 1. Compared to the cancellation circuit 122 of fig. 1, the cancellation circuit 122 performs a subtraction operation on the sensing signal S1, i.e., the sensing capacitance, to cancel part of the sensing capacitance, but the suppression circuit 822 of fig. 8 performs a division operation on the sensing signal S1, i.e., the sensing capacitance, to reduce the signal magnitude, i.e., the sensing capacitance, proportionally.

Specifically, the suppression circuit 822 is coupled between the converter 120 and the input pin P1 for suppressing the sensing signal S1 and providing the suppressed sensing signal S4 to the converter 120, so that the converter outputs the analog voltage signal VS1 according to the suppressed sensing signal S4. It should be noted that the suppression degree of the sensing signal S1, i.e., the induced capacitance, by the suppression circuit 822 may be determined according to a predetermined parameter or according to the current operating environment (e.g., the operating temperature, the average induced capacitance, etc.) of the pressure sensing circuit 82, but the invention is not limited thereto.

Referring to fig. 9, fig. 9 is a circuit diagram of the converter 120 and the suppression circuit 822 of fig. 8 according to the first preferred embodiment. As shown in fig. 9, the converter 120 may be, for example, a capacitance-to-voltage converter 900, and it includes an operational amplifier 9201 and a negative feedback circuit 9202. The inverting input terminal of the operational amplifier 9201 is coupled to the input pin P1 through the suppressing circuit 822, the non-inverting input terminal of the operational amplifier 9201 is coupled to the reference voltage Vref, and the output terminal of the operational amplifier 9201 is coupled to the adc 124. In addition, the negative feedback circuit 9202 is coupled between the inverting input terminal of the operational amplifier 9201 and the output terminal of the operational amplifier 9201, and the negative feedback circuit 9202 is formed by a first capacitor Cf and a first resistor Rf which are connected in parallel. Since the details of the capacitance-to-voltage converter 920 are as described above, they will not be described herein.

It should be appreciated that the suppression circuit 822 may be, for example, an impedance element Z coupled between the inverting input terminal of the operational amplifier 9201 and the input pin P1. The impedance device Z is used for suppressing the induced capacitance generated by the capacitive touch sensor TK1 according to the impedance value of the impedance device Z as a preset parameter, so that the capacitance-to-voltage converter 920 outputs the analog voltage signal VS1 according to the suppressed induced capacitance. Since the principle of capacitance suppression by the impedance element Z is well known to those skilled in the art, details thereof will not be further described herein.

It should also be understood that the impedance element Z may be formed by at least one passive element. That is, the impedance component Z may be not only a single resistor, a single capacitor, or a single inductor, but also any combination of the above passive components. In summary, the present invention is not limited to the specific implementation of the impedance component Z, and those skilled in the art should be able to design the impedance component Z according to actual requirements or applications. The impedance component Z may be integrated into the capacitance-to-voltage converter 920 or separately, but the invention is not limited thereto. In contrast to the cancellation circuit 122 of fig. 1, the suppression circuit 822 of fig. 9 performs a division operation to attenuate the induced capacitance. However, the above-mentioned manner of using the impedance device Z as the suppression circuit 822 is only an example, and is not intended to limit the present invention.

Referring to fig. 10, fig. 10 is a circuit diagram of the converter 120 and the suppression circuit 822 of fig. 8 according to a second preferred embodiment. As shown in fig. 10, the suppression circuit 822 may also be, for example, a voltage divider circuit including a resistor Rs1 and a resistor Rs 2. The resistor Rs1 is coupled between the inverting input terminal of the operational amplifier 9201 and the input pin P1, the first terminal of the resistor Rs2 is coupled to the node B between the resistor Rs1 and the input pin P1, and the second terminal of the resistor Rs2 is coupled to the reference voltage Vref. It should be understood that the suppressing circuit 822 of fig. 10 is used to suppress the induced capacitance generated by the capacitive touch sensor TK1 according to the impedance ratio between the resistor Rs1 and the resistor Rs2 as a preset parameter, so that the capacitive voltage converter 920 outputs the analog voltage signal VS1 according to the suppressed induced capacitance. Since the operation principle of the voltage divider circuit is well known to those skilled in the art, details thereof will not be described herein.

In addition, if it is considered that the reference voltage Vref may be, for example, the ground voltage GND, so please refer to fig. 11, fig. 11 is a circuit diagram of the converter 120 and the suppression circuit 822 of fig. 8 in the third preferred embodiment, and components in fig. 11 that are the same as those in fig. 10 are denoted by the same symbols, so that details thereof will not be further described herein. As shown in fig. 11, the suppression circuit 822 may also include a resistor Rs1, a resistor Rs2, and an operational amplifier 1101. The resistor Rs1 is coupled between the inverting input of the operational amplifier 9201 and the input pin P1. The non-inverting input terminal of the operational amplifier 1101 is coupled to the ground voltage GND, and the inverting input terminal of the operational amplifier 1101 is coupled to the output terminal of the operational amplifier 1101. In addition, a first terminal of the resistor Rs2 is coupled to the node C between the input pin P1 and the resistor Rs2, and a second terminal of the resistor Rs2 is coupled to the output terminal of the operational amplifier 1101. Since the operation principle of the suppression circuit 822 of fig. 11 is also known in the art, details thereof will not be described herein.

In summary, the touch keyboard provided in the embodiments of the present invention does not need to introduce a complicated circuit design, but only needs a simple circuit design, such as a cancellation circuit or a suppression circuit, to attenuate the sensing capacitance generated by the capacitive touch sensor, so as to avoid the overflow of the capacitive voltage converter in the pressure sensing circuit due to the reception of the excessive sensing capacitance, and also mean to increase the detection range, so that a larger sensing capacitance can be detected, and the sensitivity of the touch keyboard is improved.

The disclosure is only a preferred embodiment of the invention and should not be taken as limiting the scope of the invention, which is defined by the appended claims.