Active discharge touch key time sampling circuit architecture and integrated circuit architecture

Abstract

The utility model discloses an active discharge touch key time sampling circuit architecture and an integrated circuit architecture. The active discharge touch key time sampling circuit architecture comprises a voltage source, at least one current source and a sampling circuit, the voltage source is connected in series with a charging switch and a discharging switch, and the touch key is connected between the charging switch and the discharging switch; the current source is connected in series with the discharge switch; the sampling circuit is connected to the touch key. Therefore, a power supply can be applied to the touch key, so that the equivalent capacitance of the touch key is discharged at a constant current; the sampling circuit calculates the time change of constant current discharge, and when the discharge time exceeds the non-touched discharge time point (first discharge cut-off point), the touch key is touched by a finger, so that the accuracy of time sampling of the touch key is increased, the sensitivity of finger touch is not influenced by parasitic capacitance generated by the application environment of the touch key, and the safety of the touch key is improved. And the touch sensitivity is not influenced by parasitic capacitance leakage or residual charges of the bypass touch key.

Description

Technical Field

[0001] The utility model relates to an active discharge touch pad time sampling circuit architecture; in particular, to a circuit and integrated circuit architecture applied to a touch pad (Touch PAD) and utilizing an adjustable current source to perform touch pad time sampling. Background Art

[0002] The touch key is different from the touch screen. The touch key mainly determines whether it is touched by a finger, while the touch screen needs to locate the touch point. However, the principle is the same. The current Ic time of the capacitor discharge is related to the capacitor charge and discharge time constant (τ), such as Figure 1A and Figure 1B The voltage and current diagrams of the charging and discharging processes of the conventional touch equivalent capacitor are shown, respectively. The time constant τ=RD×C, where RD is the product of the resistance value and the capacitance value of C, and is called the time constant τ.

[0003] For example Figure 2 and Figure 3 As shown, Figure 2 is the passive discharge equivalent circuit diagram of the existing touch key, and Figure 3 is the current waveform of passive discharge. The capacitor discharge current (I CP ), it approaches 0 at the time point of 5τ. C ) changes by only a few pF, so the existing technology uses multiple charging and discharging of the touch key to accumulate the equivalent capacitance (ψ C ) to increase the accuracy of touch key time sampling. According to the discharge formula of the capacitor, the required time is ∞. In practical applications, the discharge time cannot reach ∞, so there will be residual charge, which will affect the accuracy of time sampling.

[0004] For example, in Taiwan's invention patent No. I677196, the sampling signal is a number of charge-discharge triangle waves, and the charge transfer technology is used, so there will be residual charge, which will limit the touch key load (equivalent capacitance), touch key parasitic capacitance, bypass capacitor leakage, etc. Another example is Taiwan's invention patent No. I465999, whose sampling signal is also a plurality of charge-discharge square waves, which will also increase the accuracy of touch key time sampling. Utility Model Content

[0005] In view of the lack of passive discharge of existing touch keys, the purpose of the utility model is to provide an active discharge touch key time sampling circuit and integrated circuit architecture, which can achieve the purpose of increasing the accuracy of touch key time sampling, and the sensitivity of finger touch is not affected by the parasitic capacitance generated by the touch key application environment, and the touch sensitivity is not affected by the leakage of the bypass touch key parasitic capacitance or residual charge.

[0006] To achieve the above-mentioned purpose, the utility model provides an active discharge touch key time sampling circuit architecture, adding a power supply to the touch key so that the equivalent capacitance of the touch key is discharged with a constant current; calculating the time change of the constant current discharge, when the discharge time exceeds the discharge time point when it is not touched (the first discharge cut-off point), it indicates that the touch key is touched by a finger.

[0007] To achieve the above-mentioned purpose, the utility model also provides an active discharge touch key time sampling circuit architecture, including a voltage source, at least one current source and a sampling circuit; wherein the voltage source is connected in series with a charging switch and a discharging switch, and the touch key is connected between the charging switch and the discharging switch; the current source is connected in series with the discharging switch to discharge the equivalent capacitance of the touch key with a constant current; the sampling circuit is connected to the touch key to calculate the time variation of the constant current discharge, and when the discharge cut-off time exceeds the first discharge cut-off point, it indicates that the touch key is touched by a finger.

[0008] The sampling circuit further includes: an analog-to-digital converter connected to the touch key for converting the equivalent capacitance charge and discharge current of the touch key into a digital signal; and a detection circuit connected to the analog-to-digital converter for calculating the discharge time change of the equivalent capacitance of the touch key.

[0009] The discharge time can be adjusted by adjusting the current source, so that when the current source is adjusted to be larger, the discharge time is shorter, and conversely, when the current source is adjusted to be smaller, the discharge time is longer.

[0010] When the charging switch is on and the discharging switch is off, the voltage source charges an equivalent capacitance of the touch key, and when the charging switch is off and the discharging switch is on, the equivalent capacitance of the touch key is discharged with the constant current.

[0011] Among them, it can be applied to multiple touch key circuits, LED light bars or mirror touch keys.

[0012] The invention also includes: a second current source connected in series between the voltage source and the charging switch, so that the equivalent capacitor of the touch key is charged with a constant current.

[0013] To achieve the above-mentioned purpose, the utility model further provides an integrated circuit architecture for active discharge touch key time sampling, comprising a plurality of touch keys, a charging circuit, an active discharge circuit and a sampling circuit; wherein the touch key is connected to all circuits via a touch key signal bus; the charging circuit is used to charge the equivalent capacitance of the plurality of touch keys; the active discharge circuit is used to discharge the equivalent capacitance of the plurality of touch keys with a constant current; and the sampling circuit is used to calculate the time variation of the equivalent capacitance of the plurality of touch keys being discharged with the constant current, and when the discharge cut-off time of the equivalent capacitance of any of the touch keys exceeds a first discharge cut-off point, it indicates that the touch key is touched by a finger.

[0014] It also includes: a first control circuit connected to the charging circuit, used to control the charging circuit to charge the equivalent capacitance of the multiple touch keys; and a second control circuit connected to the active discharge circuit, used to control the active discharge circuit to discharge the equivalent capacitance of the multiple touch keys with a constant current. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A and Figure 1B They are respectively the voltage and current diagrams of the charging and discharging processes of the existing touch equivalent capacitor.

[0016] Figure 2 FIG. 4 is a passive discharge equivalent circuit diagram of an existing touch key.

[0017] Figure 3 This is the current waveform diagram of the existing passive discharge.

[0018] Figure 4 This is a schematic diagram of a circuit block for active discharge touch key time sampling of the utility model.

[0019] Figure 5 This is a time sampling waveform diagram of the active discharge detection circuit of the utility model.

[0020] Figure 6 This is a timing diagram of the touch key sampling waveform of the utility model.

[0021] Figure 7 It is a circuit block diagram of an active charging embodiment of the utility model.

[0022] Figure 8 This is a sampling waveform diagram of active charging of the utility model.

[0023] Fig. 9 This is a schematic diagram of an integrated circuit block for active discharge touch key time sampling of the utility model.

[0024] Explanation of the reference numerals: 10-touch key; 11-voltage source (V); 12-charging switch (SW0); 13-discharging switch (SW1); 14-current source; 15-second current source; 20-sampling circuit; 21-analog-to-digital converter (ADC); 22-detection circuit; 30-integrated circuit; 31-touch key; 32-charging circuit; 33-active discharge circuit; 34-sampling circuit; 35-first control circuit; 36-second control circuit; 37-touch key signal bus; 38-output terminal; 51-first discharge cut-off point; 52-second discharge cut-off point. DETAILED DESCRIPTION

[0025] See also Figure 4 and Figure 5 As shown, Figure 4 FIG. 1 is a schematic diagram of a circuit block for sampling time of an active discharge touch key of the utility model. Figure 5 The utility model mainly uses an active discharge touch key 10, which is used to measure the equivalent capacitance (ψ C ) charging and discharging time sampling circuit, the circuit structure includes a voltage source (V) 11 connected in series with at least one charging switch (SW0) 12 and at least one discharging switch (SW1) 13, and also includes at least one current source 14 and a sampling circuit 20, wherein the touch key 10 is connected between the charging switch (SW0) 12 and the discharging switch (SW1) 13, and the current source 14 is connected in series between the discharging switch (SW1) 13 and a ground terminal. When the current source 14 is applied to the touch key 10, the discharge current value of the current source 14 is adjusted to make the equivalent capacitance (ψ C ) can discharge at a constant current.

[0026] The sampling circuit 20 is connected to the touch key 10 and the connection point between the charging switch (SW0) 12 and the discharging switch (SW1) 13 to calculate the equivalent capacitance (ψ C ) The time variation of the constant current discharge, when the charging switch (SW0) 12 is turned on (ON) and the discharging switch (SW1) 13 is turned off (OFF), the equivalent capacitance (ψ C ) is charged to the voltage source (V) 11, the charging switch (SW0) 12 is turned off (OFF), and the discharging switch (SW1) 13 is turned on (ON), and the equivalent capacitance (ψ C ) performs constant current discharge until the discharge cut-off time exceeds a first discharge cut-off point 51, indicating that the touch key 10 is touched by a finger. Figure 5 The first discharge cut-off point 51 is the discharge cut-off point when not touched by a finger.

[0027] Please also see Figure 4 , Figure 5 , Figure 6 As shown, Figure 6 The utility model can adjust the touch key 10 equivalent capacitance (ψ C ) of the discharge current value (I CA ), the equivalent capacitance of the touch key 10 can be increased (ψ C ), that is, the first discharge cut-off point 51, so that the accuracy of time sampling of the touch key 10 can be increased.

[0028] Depend on Figure 6 It can be seen that the equivalent capacitance (ψ C ) needs to be charged before the discharge time sampling, the charging time is 0~t0, the discharge time is t0~t1, and the sampling enable time of the touch key 10 is 0~t1. Figure 5 It can be seen that the equivalent capacitance (ψ C ) discharge time sampling is only related to the current value (I CA ), so the residual electricity of the touch key 10 does not affect the accuracy of time sampling. C ) discharge time and the equivalent capacitance value (ψ C ) is proportional to the time when the equivalent capacitance of the touch key is discharged. Wherein t0 is the start time of the equivalent capacitance discharge of the touch key, and t1 is the end time of the equivalent capacitance discharge of the touch key.

[0029] like Figure 5 As shown in FIG. 1 , the first discharge cut-off point 51 is the discharge cut-off time when the touch key 10 is not touched by a finger, and the second discharge cut-off point 52 is the discharge cut-off time when the touch key 10 is touched by a finger. When the touch key 10 is touched by a finger, due to the equivalent capacitance value (ψ C ) becomes larger, such as Figure 5 The dotted line is a voltage waveform when the touch key 10 is not touched, and the solid line is a voltage waveform when the touch key 10 is touched.

[0030] For example Figure 4 As shown, the sampling circuit 20 further includes an analog-to-digital converter (ADC) 21 and a detection circuit 22. The analog-to-digital converter 21 is connected to the touch key 10 to convert the equivalent capacitance (ψ C ) The charge and discharge current is converted into a digital signal, and the detection circuit 22 is connected to the analog-to-digital converter 21 to calculate the equivalent capacitance (ψ C )’s discharge time changes.

[0031] For another active charging embodiment of the present invention, please refer to Figure 7 and Figure 8 As shown, Figure 7 is a circuit block diagram of an active charging embodiment of the utility model, and Figure 8 The active charging circuit of the present invention further includes a second current source 15 connected in series between the voltage source (V) 11 and the charging switch (SW0) 12. When the charging switch (SW0) 12 is activated (ON) and the discharge switch (SW1) 13 is closed (OFF), the equivalent capacitance (ψ C ) can be charged with a constant current. Figure 8 As can be seen from the waveform diagram, when the equivalent capacitance (ψ C ) is charged with a constant current, the waveform of the charging time 0 to t0 will be extended and steadily rise in proportion to the voltage source (V) until it is fully charged, and the active discharge process is as described above, so that the sampling time of the touch key 10 can be further extended to increase the accuracy of time sampling.

[0032] Please see again Fig. 9 As shown, it is a schematic diagram of an integrated circuit block for active discharge touch key time sampling of the utility model. The active discharge touch time sampling architecture of the utility model can be made into an integrated circuit 30 architecture, such as an integrated circuit, which can be applied to multiple touch key circuits, LED light bars or mirror touch keys and other applications. The integrated circuit 30 includes a plurality of touch keys 31, a charging circuit 32, an active discharge circuit 33, a sampling circuit 34, a first control circuit 35 and a second control circuit 36. Among them, touch key 1, touch key 2...touch key n, the plurality of touch keys 31 are connected to a touch key signal bus 37, and the touch key signal bus 37 is connected to the charging circuit 32, the active discharge circuit 33 and the sampling circuit 34, and the first control circuit 35 is connected to the charging circuit 32 to control the charging circuit 32 to charge the equivalent capacitance of the plurality of touch keys 31.

[0033] The second control circuit 36 ​​is connected to the active discharge circuit 33 to control the active discharge circuit 33 to discharge the equivalent capacitance of the plurality of touch keys 31 with a constant current; the sampling circuit 34 is used to calculate the time variation of the equivalent capacitance of the plurality of touch keys 31 being discharged with a constant current. When the equivalent capacitance discharge cut-off time of any touch key 31 exceeds a first discharge cut-off point 51, it indicates that the touch key is touched by a finger. Finally, the sampling circuit 34 sends the detected touch key time sampling result to an output terminal 38 for output to the application device.

[0034] In summary, the active discharge touch key time sampling circuit architecture of the utility model prolongs the time sampling of the touch key by active constant current discharge to increase the accuracy. It is completely different from the existing method of multiple charge and discharge of the touch key, solves the problem of residual charge generated by multiple charge and discharge, and solves the leakage problem of the touch key parasitic capacitance and bypass parasitic capacitance due to constant discharge.

Claims

1. An active discharge touch key time sampling circuit architecture, used for charging and discharging time sampling of at least one touch key, characterized in that: The architecture includes: A voltage source, connected in series with at least one charging switch and at least one discharging switch, wherein the touch key is connected between the charging switch and the discharging switch; at least one current source connected in series to the discharge switch to discharge an equivalent capacitance of the touch key with a constant current; and A sampling circuit is connected to the touch key to calculate the time variation of the constant current discharge, so as to indicate that the touch key is touched by a finger when the touch key discharge cut-off time exceeds a first discharge cut-off point.

2. The active discharge touch key time sampling circuit architecture as claimed in claim 1, characterized in that: The sampling circuit also includes: an analog-to-digital converter, connected to the touch key, for converting the equivalent capacitance charge and discharge current of the touch key into a digital signal; and A detection circuit is connected to the analog-to-digital converter to calculate the discharge time change of the equivalent capacitance of the touch key.

3. The active discharge touch key time sampling circuit architecture as claimed in claim 1, characterized in that: The discharge time can be adjusted by adjusting the current source, so that when the current source is adjusted to be larger, the discharge time is shorter; conversely, when the current source is adjusted to be smaller, the discharge time is longer.

4. The active discharge touch key time sampling circuit architecture as claimed in claim 1, characterized in that: When the charging switch is on and the discharging switch is off, the voltage source charges an equivalent capacitance of the touch key, and when the charging switch is off and the discharging switch is on, the equivalent capacitance of the touch key is discharged with the constant current.

5. The active discharge touch key time sampling circuit architecture as claimed in claim 1, characterized in that: Can be applied to multiple touch key circuits, LED light bars or mirror touch key applications.

6. The active discharge touch key time sampling circuit architecture as claimed in claim 1, characterized in that: Also includes: A second current source is connected in series between the voltage source and the charging switch to charge the equivalent capacitor of the touch key with a constant current.

7. An active discharge touch key time sampling integrated circuit architecture, characterized in that: include: A plurality of touch keys connected to a touch key signal bus; a charging circuit connected to the touch key signal bus, for charging the equivalent capacitance of the plurality of touch keys; an active discharge circuit connected to the touch key signal bus, for discharging the equivalent capacitance of the plurality of touch keys with a constant current; and A sampling circuit is connected to the touch key signal bus to calculate the time variation of the equivalent capacitance of the plurality of touch keys when discharged with the constant current, so as to indicate that the touch key is touched by a finger when the equivalent capacitance discharge cut-off time of any touch key exceeds a first discharge cut-off point.

8. The active discharge touch key time sampling integrated circuit architecture as claimed in claim 7, characterized in that: Also includes: a first control circuit connected to the charging circuit, for controlling the charging circuit to charge the equivalent capacitance of the plurality of touch keys; and A second control circuit is connected to the active discharge circuit and is used to control the active discharge circuit to discharge the equivalent capacitance of the plurality of touch keys with a constant current.

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