CN201467099U

CN201467099U - Capacitive sensing key circuit and keyboard

Info

Publication number: CN201467099U
Application number: CN2009201326205U
Authority: CN
Inventors: 丘守庆; 许申生; 刘春光; 李鹏
Original assignee: Shenzhen CHK Technology Co Ltd
Current assignee: Shenzhen CHK Technology Co Ltd
Priority date: 2009-06-08
Filing date: 2009-06-08
Publication date: 2010-05-12
Anticipated expiration: 2019-06-08

Abstract

The utility model relates to a capacitive sensing key circuit, which comprises an internal CPU, an ADC, the SoC chip of a high-frequency signal generator and a sensing signal detection circuit. The sensing signal detection circuit comprises a sensing electrode, a first resistance, a filter capacitor, a second resistance and a rectifier diode, wherein the first resistance is connected with the sensing electrode, the filter capacitor is connected between the first resistance and the ground, the second resistance is connected with the filter capacitor in parallel and the sensing electrode is connected with the signal generator through a coupling capacitor. The output of the circuit is connected with the input of the ADC. When the key is touched by a finger, a sensing capacitor used as a high-frequency signal bypass channel is formed between the sensing electrode and the ground, so that the DC voltage output by the circuit is reduced and the touch action of the finger is confirmed after the comparison with the reference voltage stored in advance is made in the CPU. Through increasing the signal frequency and the circuit response speed, the input speed of the sensing key is greatly improved, not only the traditional single key position judgment can be realized but also sliding (or moving) change judgment can be realized, and a plurality of sensing key signals input by sliding keys and multi-keys can be processed at high speed.

Description

Capacitive induction key circuit and keyboard

Technical field

The utility model relates to the sensor key of use for electronic products, the designing technique of keyboard, and particularly a kind of capacitive induction key circuit and induction keyboard are to satisfy the needs of electronic product to high-speed induction key, keyboard.

Background technology

Common condenser type sensor key, keyboard are the essential input accessories of many electronic products, and along with development of technology, many electronic products need high sensor key of adapted input speed and keyboard.But present sensor key technology can only adapt to singly-bound and import one by one, and speed is low, and when quick point touched sensor key, two key or multikey and rolls (N-key rollover) input, sensitivity was low, and misoperation increases.And, common condenser type induced key, easily affected by environment.When environmental factors such as temperature and humidity change, can cause the unstable even drift of capacitive induction key, cause the invalid or misoperation of button.

Summary of the invention

In order to overcome existing sensor key and keyboard technique above shortcomings, the utility model provides a kind of capacitive induction key circuit and induction keyboard, it has quick point touches sensor key, feather key, two key or multikey and rolls input function, can satisfy the needs of electronic product to the high-speed induction keyboard.

The utility model capacitive induction key circuit comprises:

The SoC of one built-in CPU, ADC and high frequency signal generator (System on a Chip) chip, CPU is connected with high frequency signal generator, ADC; And,

One induced signal testing circuit, this testing circuit comprises an induction electrode, be connected in first resistance of induction electrode, be connected in the other end of first resistance and the filter capacitor between the ground, be parallel to second resistance of filter capacitor, and a rectifier diode, the negative, positive end of this rectifier diode connects induction electrode and ground respectively, induction electrode is connected to high frequency signal generator by a coupling capacitance, and the output of this testing circuit connects the input of ADC; Touch on time as finger, form a inductance capacitance between the induction electrode of described testing circuit and the ground as the high-frequency signal bypass channel, the direct voltage of described testing circuit output is reduced, and then the CPU reference voltage interior with formerly being stored in memory confirm that relatively the finger touch is arranged.

Described high frequency signal generator is presented the high-frequency signal of 50KHz-4MHz to described testing circuit.

Reference voltage in the described memory is when start, CPU gather described induced signal testing circuit output by ADC a dc voltage value.

Reference voltage in the described memory can upgrade, CPU interval in service certain hour is gathered the dc voltage value of described without finger touch induced signal testing circuit output as new reference voltage by ADC, and the reference voltage of once storing before upgrading.

Adopt the induction keyboard with the quick input function of multikey of above-mentioned sensor key circuit, comprising:

The SoC chip of one built-in CPU, ADC and high frequency signal generator, CPU is connected with high frequency signal generator, ADC; And,

At least two induced signal testing circuits, the output of each induced signal testing circuit connect the input of ADC respectively, and input all connects the output of high frequency signal generator; Wherein,

Described testing circuit comprises an induction electrode, be connected in first resistance of induction electrode, be connected in the other end of first resistance and the filter capacitor between the ground, be parallel to second resistance of filter capacitor, and rectifier diode, the negative, positive end of this rectifier diode connects induction electrode and ground respectively, and induction electrode is connected to high frequency signal generator by a coupling capacitance; High frequency signal generator is presented the high-frequency signal of 50KHz-4MHz to described testing circuit, the output voltage that detects described testing circuit by ADC changes, and then CPU and formerly be stored in the memory corresponding reference voltage relatively, determine to have or not finger touch by singly-bound signal, feather key, two key or multikey roll a plurality of key signals of input.

The utility model has adopted the SoC chip of built-in high-speed CPU, ADC, the generator that the 50KHz-4MHz high-frequency signal can be provided and high-speed counter etc., its technical measures such as response speed by improving the high-frequency signal frequency and improving the induced signal testing circuit, sensor key, keyboard input speed are significantly improved, not only can do traditional singly-bound position judgment, (or moving) variation of also can sliding judges that high speed analysis processing feather key, two key roll input, multikey rolls a plurality of sensor key signals of input.

CPU is in service, and the interval certain hour is gathered the dc voltage value of induced signal testing circuit output without finger touch as new reference voltage by ADC, and the reference voltage of once storing before upgrading.Unstable even the drift of the sensor key that this measure has avoided variations such as ambient temperature, humidity to cause, the invalid or misoperation of the button of appearance.

Description of drawings

Fig. 1 is the utility model capacitive induction key circuit theory diagram;

Fig. 2 is its induction keyboard theory diagram;

Fig. 3 is Fig. 1,2 embodiment SoC chip section parallel circuit figure;

Fig. 4 is Fig. 1, an induced signal testing circuit figure of 2.

Embodiment

Describe in detail below in conjunction with embodiment.

With reference to Fig. 1, diagram capacitive induction key circuit mainly comprises the SoC chip, is integrated with a PWM in this SoC chip module 2 (being high frequency signal generator), an ADC (analog to digital converter) 3 take place, module 2, ADC3 etc. take place with PWM and are connected in CPU 1 and high-speed counter 4 etc., CPU1; Connect an induced signal testing circuit 5 outside this SoC chip, the output of induced signal testing circuit 5 connects the input of ADC 3, and module 2 provides high-frequency signal from 50KHz-4MHz to induced signal testing circuit 5 takes place PWM.

Touch on time as finger, form a inductance capacitance between the induction electrode of described testing circuit 5 and the ground as the high-frequency signal bypass channel, the direct voltage of described testing circuit 5 outputs is reduced, and then CPU 1 confirm relatively that with the reference voltage that formerly is stored in the memory finger touch is arranged.

The induction keyboard that Fig. 2 has the quick input function of multikey comprises: the SoC chip of module 2 (being high frequency signal generator) takes place in a built-in CPU1, ADC3 and PWM, and CPU1 with PWM module 2, ADC3 etc. takes place and is connected; And, at least two induced signal testing circuits 5, the output of each induced signal testing circuit 5 connects the input of ADC3 respectively, and input all connects the output that module 2 takes place PWM.

Module 2 is presented high-frequency signal from 50KHz-4MHz to all testing circuits 5 takes place in PWM, the output voltage that detects some induced signal testing circuits 5 by ADC3 changes, and then the corresponding reference voltage of CPU1 and storage formerly is relatively, determine to have or not finger touch by singly-bound signal, feather key, two key or multikey roll a plurality of key signals of input.

Fig. 3 is that Fig. 1,2 embodiment SoC chip section parallel circuit figure .U1 are SoC chip part, module 2 (being high frequency signal generator) takes place in the built-in CPU1 of U1, ADC3 and PWM, its 7-14,19,20PIN can connect an above-mentioned induced signal testing circuit 5 outputs respectively, 3PIN is the output that module 2 takes place built-in PWM, and it is the pulse signal CMPWM. of 50KHz-4MHz that frequency can be provided

Its induced signal testing circuit 5 is as Fig. 4; This testing circuit 5 comprises: an induction electrode, be connected in first resistance R 1 of induction electrode, be connected in the other end of first resistance R 1 and the filter capacitor C7 between the ground, be parallel to second resistance R 7 of filter capacitor C7, and rectifier diode D1, the negative, positive end of this diode D1 connects induction electrode and ground respectively, induction electrode is connected to PWM by a coupling capacitance C1 module 2 outputs (3PIN of U1) takes place, and the common port of filter capacitor C7, second resistance R 7 and first resistance R 1 is the d. c. voltage signal output.

The induction electrode of each sensor key is generally sheet metal, conductive rubber etc., and they are distributed in each place, key position on the PCB, cover insulating barrier or panel above.When certain insulating barrier above the induction metal plate of finger contact, form an inductance capacitance (D1 is in parallel with diode) between this induction metal plate and the ground, this inductance capacitance is released the part high-frequency signal (or this inductance capacitance has been introduced the insertion loss) to ground as shunt capacitance, thereby causes the d. c. voltage signal of its output to descend.CPU detects magnitude of voltage after this variation by ADC, relatively can confirm to have the finger touch with its reference voltage.

Require and to carry out the various deformation design to sensor key according to product appearance, can be designed to straight line, camber line, circular arrangement, can also be designed to irregular alignment, thereby bring the use experience of various novelties in the use to the consumer.

With reference to Fig. 1,3,4, configuration SoC chip U1, module 2, ADC3, CPU1 etc. take place in its built-in PWM; It is the pwm pulse signal of 50KHz-4MHz that PWM generation module 2 can provide frequency.

The course of work of capacitive induction key circuit is as follows:

Module 2 takes place and presents the pwm pulse signal of 688KHz to induced signal testing circuit 5 in CPU1 control PWM, by ADC3 gather, the dc voltage value of described without finger touch testing circuit 5 outputs of storage is as reference voltage, and stores this reference voltage;

Touch on time as finger, form a inductance capacitance between the induction electrode of described testing circuit 5 and the ground as the pwm pulse signal bypass channel, the dc voltage value of described testing circuit 5 outputs is reduced, ADC3 detects the magnitude of voltage after this variation, relatively confirms that with the reference voltage of having stored the finger touch is arranged by CPU1.

Wherein, described induced signal testing circuit 5 comprises: an induction electrode, be connected in first resistance R 1 of induction electrode, be connected in the other end of first resistance R 1 and the filter capacitor C7 between the ground, be parallel to second resistance R 7 of filter capacitor C7, and a rectifier diode D1, the negative, positive end of this diode D1 connects induction electrode and ground respectively, and induction electrode is connected to the said PWM pulse signal by a coupling capacitance C1.

During start, the dc voltage value that CPU1 gathers described without finger touch testing circuit 5 outputs by ADC3 is as reference voltage, and storage.CPU is in service, and the interval certain hour is by the new reference voltage of dc voltage value conduct of described without finger touch testing circuit 5 outputs of ADC3 collection, and the reference voltage of once storing before the renewal.Can reduce variations such as ambient temperature, humidity like this causes reference voltage to change the misoperation of appearance.

The utility model is by improving the technical measures such as response speed of high-frequency signal frequency and improvement induced signal testing circuit, sensor key, keyboard input speed are significantly improved, not only can do traditional singly-bound position judgment, (or moving) variation of also can sliding judges that high speed analysis processing feather key, two key roll input, multikey rolls a plurality of sensor key signals of input.

Claims

1. capacitive induction key circuit is characterized in that comprising:

An induced signal testing circuit, this testing circuit comprises an induction electrode, be connected in first resistance of induction electrode, be connected in the other end of first resistance and the filter capacitor between the ground, be parallel to second resistance of filter capacitor, and a rectifier diode, the negative, positive end of this rectifier diode connects induction electrode and ground respectively, induction electrode is connected to high frequency signal generator by a coupling capacitance, and the output of this testing circuit connects the input of ADC.

2. capacitive induction key circuit according to claim 1 is characterized in that: described high frequency signal generator is presented the high-frequency signal of 50KHz-4MHz to described testing circuit.

3. the induction keyboard that has the quick input function of multikey is characterized in that comprising:

Described testing circuit comprises an induction electrode, be connected in first resistance of induction electrode, be connected in the other end of first resistance and the filter capacitor between the ground, be parallel to second resistance of filter capacitor, and rectifier diode, the negative, positive end of this rectifier diode connects induction electrode and ground respectively, and induction electrode is connected to high frequency signal generator by a coupling capacitance; High frequency signal generator is presented the high-frequency signal of 50KHz-4MHz to described testing circuit.