KR101563304B1 - Reconfigurable switched-capacitor resistor and proximity touch sensor readout circuits using the resistor - Google Patents

Abstract

The present invention relates to a reconfigurable switched capacitor register and a non-contact type touch sensor readout circuit using the same. In accordance with the present invention, a reconfigurable switched capacitor By using a resistor, the design area can be reduced, which can contribute to the miniaturization of a mobile device.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a reconfigured switched capacitor resistor and a non-contact type touch sensor readout circuit using the same.

The present invention relates to a touch sensing technology, and more particularly, to a non-contact type touch sensor lead-out circuit for determining whether an object is approaching a touch panel and a reconfigured switched capacitor register used therein.

As the demand for a user friendly interface and easy operation increases, a touch sensing technology for activating a touch panel when an object is accessed is mounted in various electronic devices. In recent years, a mobile device has been developed that can detect an object such as a finger or a stylus pen without touching the screen.

In the non-contact type touch sensing technology, a lead-out circuit that detects the change of the impedance of the panel and detects the approach of the object to the touch panel is a key factor.

However, if the type of the touch panel is changed, a corresponding reference register must be used. In the past, a plurality of resistor arrays were used to perform auto calibration. However, a large area is required for a design using a resistance array, which is not suitable for miniaturization of a mobile device, and is disadvantageous in terms of cost.

On the other hand, Korean Patent Laid-Open Publication No. 2013-0007789 (April 21, 2013, "Approach Sensing Touch System") relates to a non-contact touch sensor.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art as described above, and it is an object of the present invention to provide a method and a device for controlling a variable capacitor by using a reset capacitor capacitor which can set a final impedance according to an output waveform of a control clock, The present invention provides a non-contact type touch sensor lead-out circuit using a reset capacitor capacitor which is applicable to a touch panel of a touch panel and occupies a small area and is suitable for miniaturization of a mobile device.

According to an aspect of the present invention, there is provided a reconfigurable switched capacitor register comprising: a control clock generator for generating control clocks S ₁ and S ₂ having different phases; And the switched-capacitor resistor that is implemented as a capacitor (C _S) is connected to the turn-on or turn-off switch (Φ _1, Φ ₂₎ is by the control clock (S _1, S ₂₎ having a different phase; including, but, the control clock generator is a reference current (I _REF) based on the value cycle control clock of the _{T S (S 1, S 2} ) the output, the switched-capacitor resistor control clock of the period _{T S (S 1, S 2} ) by as the period T _S of being the switch (Φ _1, Φ ₂₎ operation, the equivalent resistance (R _eq) is the control clock (S _1, S ₂₎ of said capacitor (C _S) has a different value .

Here, the upper and lower plates of the capacitor (C _S ) are connected in an earthed manner by the operation of the switches (? ₁ ,? ₂ ) so that the charging and discharging are repeated so that the equivalent resistance (R _eq ) .

Meanwhile, the present invention provides a reconfigured switched capacitor register; And a non-contact type touch sensor circuit composed of the lead-out; and the re-touch, and the switched-capacitor resistor is connected to a node between the panel detection circuit which detects a voltage (V _X) variation of the node.

According to the present invention, the switches (PHI ₁ and PHI ₂ ) of the switched capacitor resistors are controlled to control the control clocks S ₁ and S _{2 such that} the upper and lower plates of the capacitor C _S are alternately grounded, by this to occur the equivalent resistance (R _eq) this is determined, wherein the equivalent resistance of the switched-capacitor resistor (R _eq) is dependent on the duty cycle of the switch (Φ _1, Φ _2). Thus, by setting the reference current I _REF and the control bits b ₂ , b ₁ , b ₀ of the control clock generator to set the period T _s of the control clocks S ₁ , S ₂ , the switch Φ ₁ , Phi ₂ ), the equivalent resistance Req can be determined and finally the impedance Z _REF of the readjusted switched capacitor resistor can be determined.

That is, by using the re-adjustment switched capacitor resistor instead of the existing resistor array as the reference resistor associated with the touch panel, it is easy to determine the final impedance (Z _REF ) of the reference resistor associated with other types of touch panel, The design area is reduced compared to the resistance array, which is advantageous for miniaturization of mobile devices.

1 is a block diagram illustrating a non-contact type touch sensor readout circuit according to an embodiment of the present invention;
FIG. 2 is a view for explaining the technical concept of the non-contact type touch sensor readout circuit shown in FIG. 1; FIG.
3 is a block diagram of a non-contact touch sensor lead-out circuit that includes a reset capacitor and a detection circuit.
FIG. 4 is a diagram showing the circuit configuration of the control clock generator in the readjusted switched capacitor register shown in FIG. 3, and the output waveforms of the TRUE table and the control clock of the RS latch of the control clock generator.
5 is a circuit diagram of a current source.
6 is a circuit diagram of a switched capacitor register, its equivalent circuit, and phases of switch clocks which do not overlap with each other.
7 shows a comparator used in a control clock generator;
8 is a view showing a reference register corresponding to a control clock generated according to a reference current and a control bit of a control clock generator;
9 shows the output Q, Q _B and V _CAP of the RS latch according to the control bit of the control clock generator, and the control clock output waveform of the control clock generator;
10 is a diagram showing output waveforms of the non-contact type touch sensor readout circuit according to different reference register values.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, some configurations which are not related to the gist of the present invention may be omitted or compressed, but the configurations omitted are not necessarily required for the present invention, and they may be combined by a person having ordinary skill in the art to which the present invention belongs. .

FIG. 1 is a block diagram for explaining a non-contact type touch sensor read-out circuit according to an embodiment of the present invention, and FIG. 2 is a view for explaining a technical concept of the non-contact type touch sensor lead-out circuit shown in FIG.

1 and 2, a proximity touch sensor readout circuit 100 according to an embodiment of the present invention includes a reference register 110, a detection circuit 120, and an oscillator 130 And the lead-out circuit 100 is connected to the touch panel 10.

The touch panel 10 is connected to the input signal V _in through the reference register 110. Herein, the input signal V _in may be a sine wave or a square wave having a frequency of f _{in that} is output from the oscillator 130.

Capacitance C _P is formed between the electrode T _X and R _X provided on the touch panel 10, the value of C _P is determined by the electric field (electric field) between the T _X and R _X. Where Z _P is the equivalent impedance of C _P.

If an object, such as a finger or stylus pen, approaches the touch panel 10, the electric field between the electrodes T _X and R _X will be disturbed, thereby changing the impedance Z _P.

This impedance change is reflected in the node voltage V _X, the node voltage based on the distance of the object V _X would also indicate a different voltage. Therefore, the detection circuit 120 detects the voltage of V _X and outputs it as a digital signal, so that it is possible to control the electronic device according to the approach distance of the object. Here, the node voltage V _X can be expressed by Equation (1).

ΔZ _P in Equation (1) represents an impedance change in the C _P due to electric field disturbance. If the reference impedance of the resistor (110) Z _REF = 160kΩ, the input signal _{V in = 1V, f in =} 100kHz, assuming that capacitance C _P = 10pF, and ΔC _P = 1pF of the touch panel 10, the node voltage V _X Is approximately 23.7 mV. These values are within a range that can be detected in recent integrated circuits.

The core design block in the non-contact type touch sensor lead-out circuit 100 is in the reference register 111 (Z _REF ) which can be applied to other types of touch panel 10 as well. Considering that the capacitance C _P of the general touch panel 10 is 10 pF to 50 pF, the equivalent impedance of C _{P at} the input signal f _in = 100 kHz will be 160 kΩ from 30 kΩ. That is, in order to be used in different types of touch panel 10, the reference register 110 must be programmed in the range of 30 kΩ to 160 kΩ. An easy way to implement a programmable resistor is to use a resistor array. However, resistor arrays are not suitable for on-chip solutions because they occupy a large area. To this end, in this embodiment _{, a} reconfigurable switched-capacitor resistor 110 (Z _REF ) is used instead of the resistor array as the reference resistor 110. Accordingly, the size of the reference register 110 can be remarkably reduced, and a compact non-contact type touch sensor lead-out circuit 100 can be realized.

Hereinafter, the readjusted switched capacitor register 110 (Z _REF ) used as a reference register in the non-contact type touch sensor lead-out circuit 100 shown in FIGS. 1 and 2 will be described with reference to FIG.

3 shows a block diagram of a non-contact touch sensor readout circuit including a reset capacitor 120 and a detection circuit 120. The non-

As shown in FIG. 3, the rescheduled switched capacitor register 110 includes a switched capacitor register 111 and a control clock generator 112.

The value of the switched capacitor register 111 changes according to the input of the control clock and the control clock input to the switched capacitor register 111 is output from the time-mode control clock generator 112.

The control clock generator 112 generates the control clocks S ₁ and S ₂ having the period of T _s corresponding to the control bits b ₂ , b ₁ , and b ₀ .

FIG. 4A shows a circuit configuration of a control clock generator in the readjusted switched capacitor register shown in FIG. 3, FIG. 4B shows a truth table of the RS latch of the control clock generator, (V ₀ ) of the output waveform of the inverter.

The control clock generator 112 includes a DC current source I _REF for charging and discharging, a capacitor C, and two comparators 113 and 114 and an RS latch 115.

The period of the control clock is basically set as the charging and discharging time of the capacitor. Assuming that the initial states of the switches S ₁ and S ₂ are S ₁ is on and S ₂ is off, the capacitor C is charged by the DC current I _REF . When the capacitor voltage V _CAP reaches the reference level V _H first comparator 113 and a second output V _COMP1 and _COMP2 V of the comparator 114 is at the H and L respectively, the switch S ₁ according to the Truth table of the RS latch 115 is turned oFF, S ₂ is turned on. When the capacitor C is discharged and the voltage V _CAP of the capacitor C drops to the reference level V _L of the second comparator 114 according to the off and S ₂ on of the switch S ₁ , V _COMP1 and V _COMP2 become L and H respectively Switch S ₁ is turned on, and S ₂ is turned off. The repetition of the charging and discharging process generates the control clock. Meanwhile, the period T _s of the control clock can be expressed by the following equation (2).

Where V _H is the reference voltage of the first comparator 113 and V _L is the reference voltage of the second comparator 114. Therefore, the period T _S of the control clock can be easily changed according to the change of the DC current source I _REF . Here, if the capacitance of the capacitor C is set to 200 fF and the reference current I _REF is set to 1.2 uA, the control clock frequency can be changed within the range of 6 MHz to 42 MHz.

Fig. 5 is a circuit diagram of a current source I _REF composed of a feedback amplifier, a register R _B , and a current mirror. When I _REF charges or discharges capacitor C through M ₃ and M ₅ , the reference current is given by I _REF / R _B. In addition, the current source on-off control is performed through, instead of placing a separate current source on-off switch near the capacitor C, the switch S _X and S _Y. Thus, the effect of switch channel charge injection is minimized. To charge the capacitor C, S _X is turned on and S _Y is turned off. On the other hand, during discharge, S _X is off and S _Y is on.

FIG. 6A is a circuit diagram of the switched capacitor register 111, FIG. 6B is an equivalent circuit thereof, and FIG. 6C is a phase diagram of a switch clock which does not overlap with each other.

Each capacitor C _S connected to the four control switches? ₁ ,? ₂ corresponds to an equivalent resistance R _eq . It is also charged from the top plate of the capacitor C _S and discharged from the bottom plate. Conversely, the other phase eliminates the parasitic capacitance that reduces the resistance of the switched capacitor resistor 111 critically. The output waveforms of S ₁ and S ₂ output from the control clock generator 112 correspond to these two non-overlapping phases and the output waveform of the control clock generator 112 constitutes the switched capacitor register 111 The switches? ₁ and? ₂ connected to C _S are controlled.

That is, each of the capacitors C _S constituting the switched capacitor register 111 is charged and discharged by the ground connection between the upper plate and the lower plate by turning on and off the switches? ₁ and? ₂ , The equivalent resistance R _eq of the capacitor register 111 is determined and ultimately the overall impedance Z _REF of the reset capacitor registor 110 is determined.

At this time, the equivalent resistance R _eq of the switched capacitor register 111 is determined by the operation period of the switches? ₁ and? ₂ . Therefore, when adjusting the reference current I _REF and the control bit b _2, b _1, b ₀ of the control clock generator 112 by the period of the output waveform (S _1, S ₂₎ (T _S) is determined, the switch (Φ _1, The operation period of the _second reset switch capacitor R2 can be changed to set the impedance Z _REF of the final reset switch capacitor register.

7 shows the comparators 113 and 114 used in the control clock generator 112. As shown in FIG. This circuit is capable of low-power operation by combining a pre-amplifier stage with positive feedback. The difference in input is also amplified by the preamplifier and caught on the next edge of the CK input signal when positive feedback is activated.

In the foregoing, a proximity touch sensor readout circuit (100) using a reconfigurable parasitic insensitive switched-capacitor resistor (110) has been described. In accordance with the present embodiment, the conventional resistor array is replaced with a switched capacitor register 111 which is readjusted according to the change of the control clock frequency. The control clock for controlling the switches? ₁ and? ₂ of the switched capacitor register 111 is generated in the control clock generator 112 composed of the simple current source I _REF and the capacitor C. The operation of the non-contact touch sensor lead-out circuit 100 according to the embodiment of the present invention can be verified through a CMOS 0.35um level simulation of the supply voltage of 3.3V. To minimize area and power, the capacitor C of the control clock generator 112 and the capacitor C _S of the switched capacitor register 111 are set to 200 fF and 500 fF, respectively. The reference current (I _REF ) is also set in units of 1.2 uA.

8 shows a reference register Z _REF corresponding to the control clock generated according to the reference current I _REF and the control bits b ₂ , b ₁ , b ₀ of the control clock generator 112. Z _REF (Simulated Z _REF ) obtained from the circuit simulation is also shown. The difference between theoretical and actual values is 5% for b ₂ b ₁ b ₀ = 001 and 0.42% for b ₂ b ₁ b ₀ = 111. This error is due to the non-uniform reference current interlocked with the change in the control clock frequency with respect to the required value. However, the error decreases as the control clock frequency f _s increases.

9A shows the output Q and Q _B of the RS latch 115 and the output of the V _CAP when the control bit b ₂ b ₁ b ₀ = 001 (f _s = 6 MHz) of the control clock generator 112 And the control clock output waveform of the control clock generator 112. In FIG. 9 (b) shows the output waveform when b ₂ b ₁ b ₀ = 111 (f _s = 42 MHz). In both cases, it can be seen that the node voltage V _CAP moves between the reference voltages V _H = 2.15 V and V _L = 1.15 V of the comparators 113 and 114.

10 shows the output waveforms of the shunt noncontact touch sensor lead-out circuit according to different Z _REF values (166.8 kΩ-red, 41.7 kΩ-blue, 23.7 kΩ-green). Here, the input signal V _in is a 33 kHz, 2V _pp sine wave input.

The touch panel impedance Z _P is set to 650 kΩ (red), 55 kΩ (blue), and 15 kΩ (green). As expected, the amplitude of the output waveform decreased as the reference impedance Z _REF increased and the panel impedance Z _P decreased. The amplitude of the output waveform is 1.58V _PP (red), 1.13V _PP (blue), and 0.77V _PP (green). This is suitable for driving the switched capacitor register 111 and the control clock generator 112 of the readjusted switched capacitor register 110 according to the present embodiment.

When an object such as a finger or a stylus pen approaches the touch panel 10, the distance to the object is obtained by comparing the output amplitude of the reshuffled switched capacitor register 110 with the amplitude of the reference value. The output V _X of the re-tuned switched capacitor register 110 is converted to a DC level by the low voltage AC-DC converter 121, low pass filter 122 and AD converter 123 of the detection circuit 120.

The re-tuned switched capacitor register 110 implemented by the time mode control clock generator 112 and the switched capacitor register 111 and the noncontact touch sensor lead-out circuit 100 using the reset capacitor capacitor register 110 have been described above. The readjusted switched capacitor resistor 110 according to the present embodiment is a core block of the shunt type noncontact touch sensor lead-out circuit 100.

That is, conventionally, since a reference register is used by using a resistor array, it occupies a large area of a circuit design and is not suitable for miniaturization of a mobile device. In addition, since individual reference registers have to be designed to correspond to different kinds of touch panels, there is a disadvantage in terms of cost. However, in the present invention, since the re-adjustment switched capacitor register 110 is used as the reference register, it is suitable for the implementation of the on-chip touch sensor readout circuit, and the design area can be narrowed. In addition, since the resistance value can be readjusted according to the change of the control clock frequency, it is easy to apply the touch panel 10 to different kinds of touch panels 10.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And additions should be considered as falling within the scope of the claims of the present invention.

10: Touch panel
100: Non-contact touch sensor lead-out circuit
110: Readjusted switched capacitor resistor
111: Switched Capacitor Register
112: Control clock generator
113: first comparator
114: second comparator
115: RS latch
120: Detection circuit
121: AC-DC converter
122: low-pass filter
123: AD converter
130: Oscillator

Claims (3)

A re-tuned switched capacitor resistor connected to the touch panel; And
Including but; is connected to a node between the resistor and the switched-capacitor readjust the touch panel detection circuit which detects a voltage (V _X) variation of the node
The re-tuned switched capacitor register comprises:
A control clock generator for generating control clocks (S ₁ , S ₂ ) having different phases; And
Includes; switched-capacitor resistor that is implemented as a capacitor (C _S) is connected to the turn-on or turn-off switch (Φ _1, Φ ₂₎ is by the control clock (S _1, S ₂₎ having the different phase
The control clock generator outputs the control clocks S ₁ and S ₂ of the period T _S according to the value of the reference current I _REF ,
The switched-capacitor resistor is the control, an equivalent resistance (R _eq) of being the switch (Φ _1, Φ ₂₎ by the control clock (S _1, S ₂₎ of the period T _S operation, the capacitor (C _S) By having different values depending on the period T _S of the clocks (S ₁ , S ₂ )
It is possible to determine the impedance (Z _REF ) of the readjusted switched capacitor register to correspond to the touch panel even if the touch panel is replaced,
Wherein when the impedance Z _P of the touch panel is changed according to an approach distance of the object with respect to the touch panel and the node voltage V _X is changed, the detection circuit outputs a digital signal corresponding to the node voltage V _X Wherein the electronic device is controllable according to an access distance of the object. The non-contact type touch sensor lead-out circuit using the re-tuning switched capacitor register.
The method according to claim 1,
In the switched capacitor resistor, the upper and lower plates of the capacitor (C _S ) are connected in an earthed manner by the operation of the switches (PHI ₁ , PHI ₂ ) so that charging and discharging are repeated so that the equivalent resistance (R _eq ) Non-contact touch sensor lead-out circuit using re-tuned switched capacitor resistors.
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