TWI550451B - Control systems and touch devices - Google Patents

Description

Control system and touch device

The present invention relates to a control system, and more particularly to a control system for a touch panel.

In general, the touch panel can be classified into a resistive touch panel, a capacitive touch panel, and a piezoelectric touch panel. Among these types, the piezoelectric touch panel has a high signal-noise ratio (SNR), and a touch signal with better quality can be obtained. When a sensing unit of the piezoelectric touch panel is touched once, the touch signal from the sensing unit has a signal peak. The detection circuit can use this signal peak to detect the occurrence of a touch event. Since the touch signal has the existence of an imaginary part, when the touch signal does not match the impedance of the front end of the detection circuit, an oscillating waveform that is maintained for more than one second will be generated, and the touch signal is superimposed with the oscillating waveform. When at least one sensing unit around the sensing unit is touched or the sensing unit is touched again within 1 second, the detecting circuit cannot determine the subsequent at least one signal due to the superposition of the touch signal and the oscillating waveform. Whether the peak is a touch signal or an oscillating waveform. Therefore, the detection circuit cannot correctly detect the occurrence of a touch event.

Therefore, it is desirable to propose a control system for a touch panel that can reduce the influence of an oscillating waveform to correctly detect the occurrence of a touch event.

The invention provides a control system for a touch panel having a plurality of sensing units. The control system includes a compensation circuit, a charge amplifier, and a signal processing circuit. The compensation circuit includes a complex matching impedance network. The compensation circuit receives a touch signal from a particular one of the plurality of sensing units and selects one of the plurality of matched impedance networks as a transmission path of the touch signal to generate a compensated touch signal. The charge amplifier receives the compensated touch signal from the transmit path to produce an amplified touch signal. The signal processing circuit receives the amplified touch signal and detects whether the particular sensing unit is touched according to the amplified touch signal.

The invention provides a touch device. The touch device includes a touch panel and a control system. The touch panel has a plurality of sensing units. The control system receives touch signals from a particular one of the plurality of sensing units and has a plurality of matched impedance networks. The control system selects one of the plurality of matched impedance networks as a transmission path of the touch signal, and detects whether a touch event occurs on the specific sensing unit according to the touch signal passing through the transmission path.

1‧‧‧ touch device

4‧‧‧Charger amplifier

10‧‧‧Touch panel

11‧‧‧Control system

40‧‧‧Compensation circuit

41‧‧‧Charger amplifier

100‧‧‧Sensor unit

101‧‧‧Multiplexer

400‧‧‧Multiplexer

401...404‧‧‧Matching impedance network

410‧‧‧Operational Amplifier

411‧‧‧ input capacitor

412‧‧‧Return capacitor

413‧‧‧Resistors

420‧‧‧ filter

421‧‧‧Sampling-maintaining circuit

422‧‧‧ analog digital converter

423‧‧‧ processor

C ₀ , C ₁ ‧‧ ‧ capacitor

C _x ‧ ‧ capacitor

GND‧‧‧ Grounding

L ₁ ‧‧‧Inductors

L _x ‧‧‧Inductors

N20, N21‧‧‧ nodes

N40‧‧‧ input node

N41‧‧‧ output node

P80, P81, P90, P91, P92‧‧‧ crest

R ₁ ‧‧‧Resistors

R _x ‧‧‧Resistors

Source of S‧‧‧ touch signal generation

S40‧‧‧Compensated touch signal

S41‧‧‧Amplified touch signal

S100‧‧‧ touch signal

S421‧‧‧Sampling signal

S422‧‧‧ digital signal

S423‧‧‧Control signal

Z ₀ ‧‧‧ equivalent impedance

42‧‧‧Signal Processing Circuit

S100‧‧‧ touch signal

1 is a touch device according to an embodiment of the invention; FIG. 2 is an equivalent circuit of a sensing unit; FIG. 3 is an equivalent module corresponding to a signal source of a sensing unit; A control system according to an embodiment of the present invention; FIG. 5 shows a signal processing circuit of the control system in FIG. 4 according to an embodiment of the present invention; and FIG. 6 shows a matching impedance in FIG. 4 according to an embodiment of the present invention. The circuit architecture of the network; 7A and 7B are diagrams showing a circuit structure for matching an impedance network in FIG. 4 according to other embodiments of the present invention; and FIG. 8A is a diagram showing a matching impedance network having a smaller equivalent impedance when the touch signal is in FIG. The compensated touch signal generated at the time; FIG. 8B shows the compensated touch signal generated when the touch signal passes through the matched impedance network having a larger equivalent impedance in FIG. 4; FIG. 9A is shown in FIG. The compensated touch signal that has not passed through the high pass filter; the Fig. 9B shows the compensated touch signal after the filtering operation of the high pass filter in Fig. 5; and Fig. 10 shows the control system according to another embodiment of the present invention.

The above described objects, features and advantages of the present invention will become more apparent from the description of the appended claims.

Fig. 1 is a view showing a touch device according to an embodiment of the present invention. Referring to FIG. 1 , the touch device 1 includes a touch panel 10 and a control system 11 . In the embodiment of the present invention, the touch panel 10 is exemplified by a piezoelectric type. The touch panel 10 includes a plurality of sensing units configured in an array. In the embodiment of Fig. 1, 20 sensing units arranged in a 4X5 array are taken as an example. The control system 11 is coupled to the touch panel 10 and receives touch signals from the sensing units to detect whether a touch event has occurred. The equivalent circuit of each sensing unit is like the circuit of Figure 2, which includes capacitors C ₀ and C ₁ , resistor R ₁ , and inductor L ₁ . Capacitor C ₁ , resistor R ₁ , and inductor L _{1 are} connected in series between nodes N20 and N21. The capacitor C _{0 is} coupled between the nodes N20 and N21. According to the equivalent circuit of each sensing unit in Fig. 2, the equivalent impedance Z ₀ can be obtained as:

At this time, an equivalent module corresponding to the signal source of each sensing unit is shown in FIG. 3, where S is a source indicating the generation of the touch signal.

According to the above (1), it is known that the equivalent impedance Z _{0 of} each sensing unit has an imaginary part, that is, the equivalent impedance Z ₀ has a reactance component. When the touch signal does not match the impedance of the back-end circuit, it will cause the generation of the oscillating waveform, which in turn affects the correctness of the touch detection. Control system according to embodiment 11 of the present invention optionally impedance matching network to offset the imaginary part of the equivalent impedance Z _0, the control system 11 of the touch detection operation is not affected by the oscillating waveform.

Figure 4 shows a control system 11 in accordance with an embodiment of the present invention. Referring to FIG. 4, the control system 11 includes a compensation circuit 40, a charge amplifier 41, and a signal processing circuit 42. The compensation circuit 40 includes a multiplexer 400 and a complex matching impedance network. In the embodiment of Fig. 4, four matching impedance networks 401 to 404 are taken as an example for illustration. The matching impedance networks 401~404 have different equivalent impedances from each other. In one embodiment, the equivalent impedance of the matched impedance networks 401-404 is sequentially increased. The multiplexer 400 couples the touch panel 10 to receive a touch signal and selectively transmits the touch signal to one of the matched impedance networks 401-404. The charge amplifier 41 is coupled to the matched impedance network 401-404 at the input node N40 of the charge amplifier 41. The charge amplifier 41 includes an operational amplifier 410, an input capacitor 411, a feedback capacitor 412, and a resistor 413. The positive input terminal (+) of the operational amplifier 410 is coupled to the ground GND, and the output terminal thereof is coupled to the output node N41 of the charge amplifier 41. The first end of the input capacitor 411 is coupled to the input node N40, and the second thereof The terminal is coupled to the negative input terminal (-) of the operational amplifier 410. The feedback capacitor 412 is coupled between the input node N40 and the output node N41. The resistor 413 is coupled between the negative input terminal (-) of the operational amplifier 410 and the output node N41. The circuit architecture of the above-described charge amplifier 41 is only an example. In other embodiments, charge amplifier 41 can be implemented in other circuit architectures. The multiplexer 400 is controlled by the signal processing circuit 42 to select one of the matched impedance networks 401-404 to communicate the received touch signal to the selected matched impedance network.

In an embodiment of the present invention, as shown in FIG. 5, the signal processing circuit 42 includes a filter 420, a sample-and-hold circuit 421, an analog-to-digital converter 422, and a processor 423. The operation of the control system 11 of the present invention will be described below in conjunction with Figures 4-5. It is assumed that the control system 11 is currently coupled to the sensing unit 100 to detect whether a touch event has occurred. In this case, the multiplexer 400 receives the touch signal S100 from the sensing unit 100 in FIG. For example, the multiplexer 400 selects the initial matching impedance network 401 as the transmission channel of the touch signal S100. Matching the impedance network 401 as an initial matching impedance network is only an example. In other embodiments, the initial matching impedance network is determined based on system requirements. Next, the multiplexer 400 transmits the touch signal S100 to the matching impedance network 401 such that a compensation touch signal S40 is generated at the output node of the compensation circuit 40 (ie, the input node N40 of the charge amplifier 41). The charge amplifier 41 receives the compensated touch signal S40, and performs an amplification operation on the compensated touch signal S40 to generate an amplified touch signal S41 at the output terminal N41. The filter 420 of the processing circuit 42 is coupled to the output terminal N41 of the signal charge amplifier 41 to receive the amplified touch signal S41. The filter 420 performs a filtering operation on the received amplified touch signal S41. In this embodiment, the filter 420 is a high-pass filter for performing high-pass filtering on the amplified touch signal S41 to filter out low frequencies. Minute. The sample hold circuit 421 is coupled to the filter 410 and receives the amplified touch signal S41 that has been filtered by the filter 420. The sample hold circuit 421 performs a sample hold operation on the received amplified touch signal S41, thereby generating a sample signal S421. The analog digital converter 422 is coupled to the sample and hold circuit 421. The analog-to-digital converter 422 receives the sampling signal S421 and performs an analog-to-digital conversion operation on the sampling signal S421, thereby converting the sampling signal S421 into a digital signal S422.

Referring to FIG. 5, the processor 423 is coupled to the filter 420 to receive the amplified touch signal S41 that has been filtered by the filter 420. The processor 423 calculates a signal noise ratio of the received amplified touch signal S41, and determines whether the calculated signal noise ratio is lower than a predetermined threshold, thereby controlling whether the multiplexer 400 selects another matching impedance network as Transfer channel. When the processor 423 determines that the calculated signal to noise ratio is lower than a preset threshold, the multiplexer 400 is controlled to select another matching impedance network (eg, the matching impedance network 402) as a transmission channel through the control signal S423. That is, the transmit channel is changed from the initial matched impedance network 401 to the matched impedance network 402. When the processor 423 determines that the calculated signal to noise ratio is not less than (ie, equal to or greater than) the preset threshold, the multiplexer 400 is controlled to maintain the currently selected matching impedance network as the transmission channel through the control signal S423. The initial matching impedance network 401 is still the transmission channel. When the multiplexer 400 switches to select the matching impedance network 402 as the transmission channel, the processor 423 continues to perform the above-described signal noise ratio determination operation to control whether the multiplexer 400 switches to select another matching impedance network until the signal noise The ratio is equal to or greater than the preset threshold. As shown in FIG. 5, the processor 423 is also coupled to the analog digital converter 422 and receives the digital signal S422. The processor 423 detects whether the sensing unit 100 is touched according to the digital signal S423.

In an embodiment of the present invention, each of the impedance matching network by the capacitor 401 to 404 lines C _x, resistor R _x, and the inductor L _x is composed as shown in FIG. 6. In Fig. 6, the capacitor C _x , the resistor R _x , and the inductor L _x are connected in series to each other. For each matched impedance network, due to the circuit composition, there is an imaginary part of its equivalent impedance, that is, there is a reactance component. By the selection of the matched impedance network by the multiplexer 400, the equivalent impedance imaginary part of the finally selected matched impedance network is offset from the imaginary equivalent of the equivalent impedance of the currently detected sensing unit. Therefore, the oscillating waveform can be avoided or attenuated, and the accuracy of detecting the touch can be improved. The circuit connection architecture of each matched impedance network in Figure 6 is an example. In other embodiments, the capacitor C _x R _x in series with a resistor, and connected in series with the resistor container C _x R _x L _x and then in parallel with the inductor, as shown on FIG. 7A. In still other embodiments, the capacitor C _x L _x and inductor in series, and the series inductor and the container C _x R _x L _x and then in parallel with the resistor, as shown on FIG. 7B.

According to the above, the matching impedance networks 401 to 404 have equivalent impedances different from each other and sequentially increase. Therefore, the compensated touch signal S40 generated by the touch signal S100 after passing through different matching impedance networks will also have different waveforms. Figure 8A shows the compensated touch signal S40 generated when the touch signal S100 passes through a matching impedance network having a relatively small equivalent impedance (e.g., matching the impedance network 401 or 402). Since the imaginary part is offset, the influence of the oscillating waveform on the touch signal S100 is reduced, and therefore, the compensated touch signal S40 has a distinct peak P80. The subsequent charge amplifier 41 and signal processing circuit 42 can detect a touch event occurring at the sensing unit 100 (the currently detected sensing unit) according to the peak P80. Figure 8B shows the compensated touch signal S40 produced when the touch signal S100 passes through a matching impedance network having a relatively large equivalent impedance (e.g., matching the impedance network 403 or 404). Since the imaginary part is offset, the compensation touch signal S40 has a more relative to the oscillating waveform. Prominent peak P81. The subsequent occurrence of a touch event on the sensing unit 100 can be more accurately detected by the subsequent charge amplifier 41 and signal processing circuit 42 based on the peak P81.

According to the above, the signal processing circuit 42 has a high pass filter 420 that filters out the low frequency components of the compensated touch signal S40 to obtain high frequency components for touch detection. Figure 9A shows the compensated touch signal S40 that has not passed through the high pass filter 420. Fig. 9B shows the compensated touch signal S40 after the filtering operation by the high pass filter 420. In FIG. 9A, the peak P90 indicates that a touch event has occurred at the sensing unit 100 (the currently detected sensing unit). When the compensated touch signal S40 passes through the high pass filter 420, it is indicated that the peak P91 at which the touch event occurs in the sensing unit 100 clearly has a large amplitude, as shown in FIG. 9B. In Fig. 9B, there is additionally a peak P92. The peak P92 that first appears in the compensated touch signal S40 is an unwanted signal generated by zero-padding when the length of the sampled data does not match the filter length in the filtering operation. Therefore, in the signal processing circuit 42, the first peak P92 can be ignored by a simple signal processing method, whereby the occurrence of a touch event can be accurately determined based on the peak P91.

In another embodiment of the invention, control system 11 further includes multiplexer 101, as shown in FIG. The multiplexer 101 is coupled between the touch panel 10 and the compensation circuit 40. The multiplexer 101 is selectively coupled to a sensing unit and the compensation circuit 40. The multiplexer 101 transmits a corresponding touch signal to the compensation circuit 40 to perform the above-described matching impedance network selection operation and the detection operation of the subsequent touch event occurrence. The multiplexer 101 can determine the order in which it selects the sensing unit according to the system settings.

According to various embodiments of the invention described above, the invention provides The impedance network is matched and an appropriate matching impedance network is selected as the transmission channel for the touch signals from each of the sensing units. In this way, the oscillation waveform due to the impedance mismatch can be avoided or weakened, so that the signal processing circuit 11 at the back end can more accurately determine whether a touch event occurs on the corresponding sensing unit.

The present invention has been disclosed in the above preferred embodiments, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can make a few changes without departing from the spirit and scope of the invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

11‧‧‧Control system

40‧‧‧Compensation circuit

41‧‧‧Charger amplifier

400‧‧‧Multiplexer

401...404‧‧‧Matching impedance network

410‧‧‧Operational Amplifier

411‧‧‧ input capacitor

412‧‧‧Return capacitor

413‧‧‧Resistors

GND‧‧‧ Grounding

N40‧‧‧ input node

N41‧‧‧ output node

S40‧‧‧Compensated touch signal

S41‧‧‧Amplified touch signal

S423‧‧‧Control signal

42‧‧‧Signal Processing Circuit

S100‧‧‧ touch signal

Claims (17)

A control system for a touch panel, the touch panel having a plurality of sensing units, comprising: a compensation circuit comprising a complex matching impedance network, wherein the compensation circuit receives a specific sense from the sensing units Measuring a touch signal of the unit, and selecting one of the plurality of matched impedance networks as a transmission path of the touch signal to generate a compensation touch signal, wherein the compensation circuit further comprises: a first multiplexer, Coupling the matched impedance network and receiving the touch signal, wherein the first multiplexer selectively transmits the touch signal to one of the matched impedance networks to generate the compensated touch signal; a charge amplifier that receives the compensated touch signal from the transmission path to generate an amplified touch signal; and a signal processing circuit that receives the amplified touch signal and detects whether the particular sensing unit is touched based on the amplified touch signal. The control system of claim 1, wherein the signal processing circuit calculates a signal to noise ratio of the amplified touch signal, and determines that the value of the signal noise ratio is lower than a threshold value, the signal processing The circuit controls the compensation circuit to select the other of the matched impedance networks as the transmission path. The control system of claim 1, wherein the matched impedance networks have different equivalent impedances. Such as the control system described in claim 1, wherein each of the horses The impedance network includes a capacitor, an inductor, and a resistor. The control system of claim 1, wherein the signal processing circuit comprises: a filter receiving the amplified touch signal and performing a filtering operation on the amplified touch signal; and a processor receiving the The amplified touch signal of the filter calculates a signal noise ratio of the amplified touch signal, and determines whether the value of the signal noise ratio is lower than a threshold value; wherein, when the processor determines the value of the signal noise ratio Below the threshold, the processor controls the compensation circuit to select the other of the matched impedance networks as the transmission path. The control system of claim 5, wherein when the processor determines that the value of the signal noise ratio is not less than the threshold, the processor controls the compensation circuit to maintain the currently selected matching impedance network. As the transmission path. The control system of claim 5, wherein the signal processing circuit further comprises: a sample maintaining circuit, receiving the amplified touch signal from the filter, and performing a sample maintaining operation on the amplified touch signal to Generating a sample signal; and an analog-to-digital converter receiving the sampled signal and performing an analog-to-digital conversion operation on the sampled signal to generate a digital signal; wherein the processor receives the digital signal and, based on the digital signal It is detected whether the specific sensing unit is touched. The control system of claim 5, wherein the filter is a high pass filter. The control system of claim 1, wherein the charge amplifier comprises: an operational amplifier having a positive input terminal, a negative input terminal, and an output terminal, wherein the positive input of the operational amplifier And the output end is coupled to a ground and an output node; an input capacitor has a first end and a second end, wherein the first end and the second end of the input capacitor are respectively coupled to an input a node and the negative input terminal of the operational amplifier; a feedback capacitor coupled between the input node and the output node; and a resistor coupled to the positive input terminal of the operational amplifier and the output node The input node receives the compensated touch signal, and the amplified touch signal is generated at the output node. The control system of claim 1, further comprising: a second multiplexer coupled between the touch panel and the compensation circuit; wherein the second multiplexer selectively treats the One of the sensing units is coupled to the compensation circuit, and the one of the sensing units serves as the specific sensing unit. A touch device includes: a touch panel having a plurality of sensing units; a control system, receiving a touch signal from a specific sensing unit of the sensing units, and having a complex matching impedance network; wherein the control system comprises: a multiplexer coupled to the matched impedance network Receiving the touch signal, wherein the multiplexer selects one of the matched impedance networks as a transmission path of the touch signal; wherein the control system detects the touch signal according to the touch signal through the transmission path Whether a touch event occurs on a particular sensing unit. The touch device of claim 11, wherein the control system comprises: a compensation circuit comprising the multiplexer and the matched impedance network, receiving the touch signal, and according to the transmission path The touch signal generates a compensated touch signal; a charge amplifier receives the compensated touch signal from the transmission path to generate an amplified touch signal; and a signal processing circuit receives the amplified touch signal and according to the amplified touch signal A touch event is detected on the particular sensing unit. The touch control device of claim 12, wherein the signal processing circuit comprises: a filter that receives the amplified touch signal and performs a filtering operation on the amplified touch signal; and a processor that receives the The amplified touch signal of the filter calculates a signal noise ratio of the amplified touch signal, and determines whether the value of the signal noise ratio is lower than a critical value; Wherein, when the processor determines that the value of the signal to noise ratio is lower than the threshold, the processor controls the compensation circuit to select the other of the matched impedance networks as the transmission path. The touch device of claim 13, wherein when the processor determines that the value of the signal noise ratio is not less than the threshold, the processor controls the compensation circuit to maintain the currently selected matching impedance network. The road serves as the transmission path. The touch control device of claim 13, wherein the signal processing circuit further comprises: a sample maintaining circuit, receiving the amplified touch signal from the filter, and performing a sample maintaining operation on the amplified touch signal To generate a sampled signal; and an analog to digital converter. Receiving the sampling signal, and performing an analog-to-digital conversion operation on the sampling signal to generate a digital signal; wherein the processor receives the digital signal, and detecting whether a touch event occurs on the specific sensing unit according to the digital signal. The touch device of claim 13, wherein the filter is a high pass filter. The touch device of claim 11, wherein each of the matched impedance networks comprises a capacitor, an inductor, and a resistor.