WO2003094352A1

WO2003094352A1 - Indirect touch switch for electrical apparatus

Info

Publication number: WO2003094352A1
Application number: PCT/KR2002/001978
Authority: WO
Inventors: Soon-Hyeong Kwon; Woon-Jin Lee
Original assignee: ESSDESIGN CORP Ltd
Current assignee: ESSDESIGN CORP Ltd
Priority date: 2002-05-02
Filing date: 2002-10-23
Publication date: 2003-11-13
Anticipated expiration: 2004-11-02
Also published as: AU2002348585A1

Abstract

The present invention discloses an indirect touch switch sensing the finger touch from the change of measured capacitance, which can be invisibly installed at the inner panel of an electrical apparatus or a wall switch as an on/off switch, an volume control switch, and a control switch, etc.

Description

TITLE OF INVENTION INDIRECT TOUCH SWITCH FOR ELECTRICAL APPARATUS

FIELD OF THE INVENTION The present invention relates to a indirect touch switch for electric apparatus, and more particularly to an electric apparatus equipped with the indirect touch switch and/or a wall switch which senses the change of capacitance due to the touch of human fingers.

DESCRIPTION OF THE RELATED ART Most of the electric apparatus is equipped with switches for operational manipulation. A variety of switches are employed in accordance with the utility and shape of the appliances.

Recently, the switches become an important factor in the design of product because the home appliances affects the interior design as well as the use. As a consequence, the switches for volume control, channel select, and chromaticity control are arranged in the rear or in the invisible location of the appliances. In other words, it is even required, the electronic switches of the appliances are arranged in such a way that they are invisible or not noticeable.

FIGS.1A and IB are schematic diagrams for indirect touch switch according to the prior art. The prior art illustrated in FIG.1A reveals an indirect touch switch having a groove in the external frame 2' of the appliance and

I D metal region 4' protruded in the groove.

In the upper part of the metal region 4 ' , an insulating film 6 is formed. If the fingers 1 of human body get in touch with a certain region of the insulating film 6, an electronic

1 5 circuit 5 senses the change of the charge at the metal region 4 ' .^'

In this case, the prior art employs the acrylic resin of which the thickness should be kept below 1mm in order to increase the sensitivity. Consequently, the prior art depicted in FIG 1A has a shortcoming in that the strength and durability of the insulating film 6 are poor .

In the meanwhile, the prior art, depicted in FIG. IB, has a protruded metal part ' for its contact to the groove formed in the frame 2' . When the protruded metal part is in contact with the fingers, the change of the capacitance is detected.

The prior art, depicted in FIG. IB, however, has a shortcoming in that malfunction or operational failure can occur due to the insertion of alien substance between the external frame 2 ' and the protruded metal part

DETAILED DESCRIPTION OF THE INVENTON

Therefore, it is an object of the present invention to provide an indirect switch performing the function of the conventional switch even with being exposed to the exterior of the appliance.

It is also an object of the present invention to provide a wall switch or an electrical appliance having an indirect touch switch operating with a sensor sensing the change of capacitance when the switch is in contact with the human body.

In order to fulfill the goals of the present invention, the present invention discloses a detector for detecting the touch or the approach of the human body at the backside of the front panel of the appliance, and an oscillator producing the oscillation frequency varying with the change of the capacitance detected at the detector. The present invention further comprises a rectifier converting the output of the oscillator to a dc voltage, and a differential amplifier for the amplification of the dc voltage at the output of the rectifier.

The present invention further comprises a signal generator for comparing the output of the differential amplifier with the reference voltage .

The present invention also provides a wall switch having a control board comprising a dielectric plate for the contact or the approach of a human body, a metal plate arranged with a predetermined spacing in parallel to the dielectric plate, and an on/off control circuit in electrical connection to the metal plate.

The control board in accordance with the present invention comprises a sensor detecting the change of static capacitance, switching circuit for on/off control in connection with the power line to the wall switch, switching control unit controlling the operation of the switching circuit under the control of the signal from the sensor, and a rectifier for supplying a dc power to the sensor and the switching control unit . BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention will become apparent from a detailed description of the specification taken in conjunction with the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only.

In the drawings :

FIGS .1A and IB are schematic diagrams of an appliance equipped with the indirect touch switches of the prior art.

FIG.2 is a schematic diagram of an appliance equipped with an indirect touch switch in accordance with a first embodiment of the present invention.

FIG.3 is a schematic diagram of an appliance equipped with an indirect touch switch in accordance with a second embodiment of the present invention.

FIG. is a schematic diagram illustrating a preferred embodiment of an indirect touch switch in accordance with the present invention. FIGS.5A through to 5D are schematic diagrams illustrating preferred embodiments of electrical appliances equipped with indirect touch switches such that those switches are invisible from the outside.

FIG.6 is a schematic block diagram illustrating the construction of the sensor circuit in accordance with the present invention

FIG.7 is a schematic diagram illustrating the detecting unit for detecting the change of the static capacitance.

FIG.8A is a schematic diagram illustrating the waveform of the output signal, transformed into a square wave, and a sensing signal applied to the waveform shaping circuit in FIG.7

FIG.8B is a schematic diagram illustrating the waveform of the saw-tooth reference signal (ref_in) and a square-wave reference signal (f_ref_in) .

FIG.9 is a schematic diagram illustrating the block of the determining unit in accordance with a preferred embodiment of the present invention.

FIG.10 is a schematic diagram illustrating a wall switch as a third embodiment of the present invention. FIG.11 is a schematic diagram illustrating a wall switch employing the change of the capacitance in accordance with the present invention.

FIG.12 is a schematic circuit diagram illustrating the sensor unit for detecting the change of the static capacitance.

FIG.13 is a schematic diagram illustrating the construction of a switch control unit in accordance with a third embodiment of the present invention.

FIG.14 is schematic circuit diagram illustrating the switching unit and the rectifier in accordance with a third embodiment of the present invention.

FIG.15 is a schematic diagram illustrating the construction of wall switch in accordance with a fourth embodiment of the resent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

OF THE INVENTION

The present invention will be explained in detail with reference to the accompanying drawings .

FIG.2 is a schematic diagram illustrating the concept of an electric appliance equipped with an indirect touch switch in accordance with a first embodiment of the present invention.

Referring to FIG.2, if a user puts his fingers 1 on a certain region of the external frame 2 of an electric appliance, there is a change in the stored charge of the metal unit 4 due to the capacitance of the human being. As a consequence, a capacitance- sensing circuit 5 detects the indirect touch of a human body.

The indirect touch switch in accordance with a first embodiment of the present invention, as depicted in FIG.2, has a metal unit 4 in contact with the printed circuit board (PCB; 3) and make electrical connections between the metal unit 4 and the sensing circuit 5.

In this case, the thickness of the external frame 2 can be approximately 3mm and the acrylic resin or plastic and glass can be employed .

FIG.3 illustrates another embodiment of an indirect touch switch comprising and external frame 2 with a different material for the cover frame 2¹' on the metal sensing circuit 4. Preferably, the thickness of the cover frame 2'' could be above than 3mm. FIG.4 is a schematic diagram illustrating an indirect touch switch having a sensing circuit in accordance with the present invention .

Referring to FIG.4, the static capacitance detected at the touch detecting unit 10 is changed if the fingers get close to or in touch with the switch. As a consequence, the oscillating frequency of the oscillator 20 is changing and the oscillating signal of the oscillator 20 is rectified to a dc voltage at the rectifying unit 30, and followed by a step of differential amplification with reference to a predefined voltage at a differential amplifier 40.

In addition, the output voltage of the differential amplifier 40 is compared with the predefined reference voltage at a comparator 50 in order to generate a switching signal when the fingers get close to or in contact with the switch .

Referring to FIG. again, an indirect touch switch in accordance with the invention comprises a touch detector 10, detecting the change of capacitance when the fingers get close to or in contact, an oscillator 20 generating a signal whose oscillation frequency is varying with the change of- the capacitance, and a rectifying circuit 30 converting the output of the oscillator 20 to a de voltage.

In addition, the present invention further comprises a comparator 50 generating a switching signal by comparing the dc voltage of the differential amplifier 40 with the predetermined reference voltage .

The touch sensing circuit, depicted in

I t) FIG.4, does not necessarily comprise an oscillator 20, rectifying circuit 30 and a differential amplifier 40.

The technique for a touch sensing circuit is disclosed in Korean Patent No. 342,

15 736.

FIG.5A is a schematic diagram illustrating an embodiment wherein an indirect touch switch is implemented in the interior of the flat-panel television monitor. 0 Referring to FIG.5A, the present invention comprises an indirect touch switch 96, an on/off detecting unit for power control 60, a detecting unit for volume up control 70, a detecting unit for volume down control go, and a touch detector for channel select 90, 95.

An insulating film 97 is put on the touch detector 60, 70, 80, 90, 95, while the cover 97 is aligned with the external panel of the flat-panel television monitor.

Here, when the user put his fingers close to or in touch with a certain region of the external panel which is the on top of a specific touch detector, the touch detector detects the change of capacitance.

The electric appliance equipped with the indirect touch switch in accordance with the present invention can be applied to other various home appliances as well as the television monitors.

FIGS.5B through 5D are schematic diagrams illustrating preferred embodiments of implementing indirect touch switches invisibly inside the electric appliances.

A various switches are implemented inside the panel of electrical appliances including a microwave oven , a refrigerator, and a television set.

FIG.6 is a schematic diagram illustrating a sensing circuit in accordance with a preferred embodiment of the present invention .

Referring to FIG.6, the present invention comprises a capacitance detector 100 producing a square-wave signal of which the frequency is varying with the capacitance, a unit 200 detecting an indirect and/or direct touch of a human body by comparing the square- wave signal with the reference signal, and a delay circuit 300 which delays the output of the unit 200 for the stable circuit operation.

The capacitance detector 100 comprises a reference current generator 110 for supplying a static current, a saw-tooth wave generator 120 generating a saw-tooth alternating signal in accordance with the reference signal (Cap_ref ) and the sensed signal (Cap_sen) at the input, and a waveform shaping unit 130 for converting the saw-tooth signal to the square wave signal. Preferable, the waveform shaping unit 130 includes the oscillating unit 140 at the output.

The oscillating unit 140 helps to provide a stable square wave signal by supplying a feed-back the output to the saw-tooth generator 120.

In the meanwhile, the current generator 110 comprises a current mirror sense amplifier in order to generate a constant current .

The saw-tooth waveform generator 120 employs the charging and discharging of the capacitor wherein the frequency of the saw-tooth waveform is varying according to the capacitance of the sensed signal (Cap_sen) and the reference signal (Cap_ref ) . The condition for the frequency conversion can be altered in accordance with the internal construction of the oscillation unit 140.

Additionally, a reset signal (not shown in the FIGURE) can be utilized in order to initialize the point where the reference signal (Cap_ref ) and the sensed signal (Cap_sen) are compared .

The waveform shaping unit 130 converts the saw-tooth wave to a square wave, producing a high-level voltage when the voltage of the sawtooth wave is above the reference high level (VH) while producing a low-level voltage when vice versa. As a preferred embodiment, a Schmitt triggering circuit can be employed.

An oscillating unit 140 is connected to a multiple of inverters in series, and comprises a ring oscillator which forms a closed loop by connecting the output of the last stage to the input of the first stage.

In this case, the output of the odd number stage is fed back to the input of the saw-tooth generator 120.

A decision unit 200 comprises a frequency converter 210 converting the out the output of the oscillator 140 to the low frequency, a comparator 220 deciding the human touch at the input by comparing the sensed signal with reference signal through a frequency converter 210, and a reset-signal generator 230 with utilizing the signals form the frequency converter 210.

The frequency converter 210 can be implemented with a multiple of flip-flops in order to increase the sensitivity by decreasing the frequency of the sensed signal and the reference signal. The comparator 220 outputs the signal and the delay part 300 delays the output of the comparator 220 for the stable operator.

FIG.7 is a schematic diagram illustrating the block of the capacitance detector 100 in accordance with the present inven io .

Referring to FIG.7, the sensing circuit in accordance with the present invention comprises a reference current generator 110 for a constant current source, a saw-tooth wave generator 120 for generating the saw-tooth wave in accordance with the sensed signal (Cap_sen) and the reference signal (Cap_ref ) , and a waveform converter 130 for converting the saw- tooth waveform to a square wave .

A waveform converter 130 comprises a first waveform converter 131 for converting the saw-tooth sensed signal (Sen_in) to a square wave, a second waveform converter 132 for converting the saw-tooth waveform (ref_in) to a square wave .

Preferabely, the first and second waveform converters 131, 132 can be implemented with the Schmitt Trigger Circuit .

In addition, an oscillator 140 for oscillating an ac square wave comprises a first oscillating unit 141, and a second oscillating unit 142 for oscillating a reference signal.

The first and second oscillating units 141, 142 are fed back to the saw-tooth waveform generator 120.

Finally, a square wave second signal (f_sen_in) is generated through a first oscillating unit 141, while the square wave reference (r_ref_in) is generated at a second oscillating unit 142.

FIG.8A is a schematic diagram illustrating the sensed signal (sen_in) applied at a waveform converter 130 and the converted square wave (f__sen_in), while FIG.8B illustrates the waveforms of the saw-tooth reference signal (ref_in) and the square wave reference signal (f__ref_in) .

Referring to FIGS.8A and 8B, when the saw-tooth wave sensed signal (sen_in) and the saw-tooth wave reference signal (ref_in) reach their maximum, the output signal of high state is generated.

Now, when the minimum is reached, the output signal becomes low. The time point of the conversion can be adjusted by changing the value of the internal device in Schmitt Trigger circuit .

FIG.9 is a schematic diagram illustrating the sensing circuit of the decision unit 200. Referring to FIG.9, the decision unit 200 comprises a frequency converter 210 for converting the frequencies of the square-wave sensed signal (f_sen_in) and the square-wave reference signal (f_ref_in) down to the low frequency, a comparator 220 comparing the output signals of the frequency converter 210 and a generator for a reset signal 230.

A frequency converter 210 comprises a frequency converting unit for a sensed signal 212, a frequency converting unit 214 for a square wave reference signal (f_ref_in) .

Finally, the comparator 220 compares a low- frequency sensed signal (f_sen_out) of the frequency converting unit 212 for a sensed signal with a low- frequency reference signal (f_ref_out) of the frequency converting unit 214 for the reference signal, and if there is a difference in the frequency, the output signal (Out_sen) is generated because it is regarded as if the fingers are in contact with the switch.

A reset-signal generator 230 generates a reset signal (Reset) by employing a signal of the reference signal frequency converter 214, and provides the reset signal to the frequency converting unit 212 for a sensed signal, the frequency converting unit 214 for a reference signal, and the comparator 220.

In addition, a reset signal is also supplied to the saw-tooth waveform to synchronize for the stable operation of the circuit .

FIG.10 is a schematic diagram illustrating another embodiment of a wall switch Referring to FIG.10, the wall switch has a dielectric plate 44 on the switch frame 410, and a metal plate 412 is arranged at uniform intervals underneath the dielectric plate 411.

Preferably, the power switch will turned on and off depending on the change of capacitance due to the induced charge at the metal plate .

Referring to FIG.10 again, a plastic plate 413 supporting and housing the metal plate 412, a control board 415 controlling the on and off of the power, and plastic housing 414.

In accordance with a preferred embodiment of the present invention, a signal input 416 of the control board 415 is electrically connected to the metal plate 412 through the plastic plate 413.

As another preferred embodiment in accordance with the invention, the dielectric plate 411 can be of any shape including planar, three-dimensional, and/or album-like, etc. In other words, the dielectric plate can be of an arbitrary shape for the interior design.

The wall switch in accordance with the present invention can detect the change of capacitance by directly touching the switch or by proximity of a human body.

More preferably, the dielectric plate 411 can be omitted, and the change of capacitance can be detected by directly making the metal plate 412 in contact with the human being .

In addition, in case when a metal plate 412 is employed for a wall switch, the change in resistance can be utilized instead of capacitance .

Referring to FIG.10 again, a metal plate 412 is implemented on the input terminal of the PCB 415, where a plastic cover 411 is put as for a touch pad. The value of the reference capacitance, which is used for the comparison with the capacitance change when the human body is in proximity or in contact, can be set depending on the area or the dielectric constant of the touch pad. Therefore, the indirect touch wall switch 410 can be converted in to various forms .

More preferable, for a wall switch having a touch pad with a size of the conventional wall switch, the reference capacitance Q is set in such a way that there is no output if the human body is neither in proximity nor in contact .

In case when a plastic cover 411 is covered on the metal plate 412 whose capacitance is smaller than that of the referenceC, _< the capacitance sensor 420 detects the capacitance change when the human body is in proximity (4 ~ 5 cm) or in contact .

Preferably, the value of Q_^ can be set 15 pF .

FIG.11 is a schematic diagram illustrating a wall switch in accordance with a third embodiment of the invention. The capacitance sensor 420 generates an oscillating signal as a capacitance for a reference, and detects the proximity or the contact of the human body by calculating the capacitance.

The capacitance sensing unit 420 comprises an oscillating circuit converting the sensed capacitance into a square wave, a decision unit for deciding whether the human body is in proximity/contact or not, and a delay circuit for prohibiting the malfunction.

Referring FIG.11 again, a switch control unit 430 is a device wherein a signal for controlling the on/off of the switch supplying the power in a toggle manner from the capacitance sensing unit 420. In addition, the switching unit 440 is a device wherein the power supply to the lightening 470 is controlled by turning on and off the power supply.

FIG.12 is a schematic diagram illustrating the circuit for a wall switch in accordance with a third embodiment of the present invention. Referring to FIG.12, the capacitance sensing unit 420 senses the change in capacitance, either direct or indirect, and works as a switch especially when it is used as an indirect witch despite the fact that glass or a plastic layer is coated on the surface of the contact for protection.

The processing unit 502 consisting of the capacitance sensing unit 420 an oscillating circuit converting the capacitance into a square wave through an input terminal 411 of a sensing circuit, a decision unit for deciding the proximity and/or contact, and a delay circuit for avoiding the malfunction.

Referring to FIG.12, the processing unit 502 is a circuit generating an oscillation signal from the capacitance value of a certain reference value and detecting the proximity or the contact of a human body by comparing the oscillation frequency of the detected capacitance .

In the meanwhile, Q 501 is a reference capacitance for detecting the proximity and contact of a human body, which is determined by the contact area and the texture of the contact layer. Preferably, a relatively large value of capacitance can be taken because the area of the wall switch is large.

By choosing Q_.. as several and tens of several picofarads, the output of Sense 1 can be set as zero while the output of Sense 1 is unity when in contact .

FIG.13 is a schematic diagram illustrating the circuit of a switch control unit in accordance with a third embodiment of the present invention.

Referring to FIG.13, the switch control unit is a unit generating the on/off control signal for toggling the light bulb, and output 1 and O in a repeated manner by connecting the input D and the output Q of the flip-flop 504.

FIG.14 is a schematic diagram illustrating a switching unit and a rectifying unit for a wall switch in accordance with a third embodiment of the present invention.

Referring to FIG.14, and AC signal is converted to a DC signal of 6.8V through BDl 510, R2 511, C2 512, DZ3 513, C3 514, and supplies power to the switch control unit 430 and switching unit 440.

Additionally, the control signal controls the on and off of switching control resister (SCR) S-_L 517 through a photocoupler UI 515 and Ql 516. When Ql 516 is off, the voltage of gate (terminal 3) of XI 518 becomes on, and XI 418 is also turned on. Finally, the light bulb becomes on because power is supplied to node 402 through terminals 1, 2 of XO 119, node 403, and terminals 1, 2 of XI 518.

FIG.15 is a schematic diagram illustrating a wall switch employing the change of resistance employing the change of resistance in accordance with a fourth embodiment of the present invention. Referring to FIG.15, the embodiment employs the change in resistance and also a change in voltage drop as a consequence which is amplified by an amplifier 600 and compared at a comparator 610 when a human body is in proximity or in contact .

The touch unit 411 denotes the resistance value in parallel due to the contact of a human body, and the change in voltage drop is amplified through an amplifier 600 and compared by a comparator 610. Additionally, the adjustment unit for reference 630 adjusts sensitivity .

The output of the reference adjustment unit 610 can be filtered 620 in order to compensate for the movement of the output during contact .

Although the invention has been illustrated and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention.

Therefore, the present invention should not be understood as limited to the specific embodiment set forth above but to include all possible embodiments which can be embodies within a scope encompassed and equivalents thereof with respect to the feature set forth in the appended claims.

INDUSTRIAL APPLICABILITY The indirect touch switch in accordance with the present invention makes it possible to design the interior beautiful by hiding the switch at the backside of the front panel of the appliances .

Claims

WHAT IS CLAIMED IS: 1. An electric appliance having a touch detector arranged at the invisible side of the external frame for detecting the change of capacitance due to either the proximity or the contact of a human body, and further comprising a switching signal generating circuit for detecting the change of static capacitance due to the charge induced at said touch detector.

2. The electric appliance as set forth in Claim 1 wherein an insulating layer is included between said touch detector and the external frame .

3. The electric appliance as set forth in Claim 1 wherein the capacitance is changed due to the capacitance of a human body when a certain region of the external frame is touched and the switching circuit for detecting the change of capacitance is invisibly arranged.

4. The electric appliance as set forth in Claim 1 wherein said touch detector is in contact with the inner side of the external frame, and the change in capacitance detected at said touch detector is fed to an oscillator producing a waveform with different oscillating frequency for deciding the proximity or the contact of a human body by comparing the frequencies.

5. A wall switch having a control board comprising a power control circuit electrically in contact with a metal plate spaced with a predetermined distance and aligned in parallel with a dielectric plate for sensing the proximity and contact of a human body wherein said control board comprising: a capacitance sensing unit for converting the capacitance change into on/of electrical signal by detecting the capacitance; a switching unit for turning on and off the power supply to the power line for the wall switch a switching control unit controlling the operation of said switching unit by taking the signal from said capacitance sensing unit; and a rectifying unit for supplying a dc power supply to said capacitance sensing unit and said switching control unit.

6. The wall switch as set forth in Claim 5 wherein said dielectric plate is a plastic plate .

7. The wall switch as set forth in Claim 5 wherein said dielectric plate is either planar or of a three-dimensional shape.

8. The wall switch as set forth in Claim 5 wherein said capacitance sensing unit produces a reference oscillating signal (a first oscillating signal) with a predefined reference capacitance and an instantaneous oscillating signal (a second oscillating signal) in accordance with the value of the capacitance change when a human body is in proximity or in contact while the change between said first and second oscillating signals in above a threshold, the output of said capacitance sensing unit is toggled

9. The wall switch as set forth in Claim 5 wherein said switching control unit comprises a

D-flipflop whose input (D) and output bar ( Q ) are tied together in order to form a toggle switc .

10. The wall switch as set forth in Claim 5 wherein a control signal is taken through a photocoupler in order to control a switching control resistor (SCR) and a trister for connecting power line is included.

11. The wall switch as set forth in Claim 5 wherein said dielectric plate is omitted, and said metal plate is implemented such that it is in contact with a human body.

12. A wall switch having a control board comprising a power supply control circuit electrically connected to a metal plate designed for direct touch with a human body wherein said control board comprising: an voltage amplifier amplifying the voltage change due to the resistance change when said metal plate is in contact; a comparator to detect the voltage change at the metal plate by comparing the output of said amplifier and reference voltage; a filter for filtering the noise component of said comparator; a switching unit for supplying the power to the power line; and a control unit controlling the operation of said switching unit by taking the signal from the f i 11er .

13. The wall switch as set forth in Claim 5 wherein said switch functions as a frame.

14. The wall switch as set forth in Claim 5 wherein said switch functions as an interior device .