TWI893692B - Temperature sensing device and temperature sensing method - Google Patents

Abstract

A temperature sensing device includes an output circuit and an operating circuit. The operating circuit generates, in response to a current signal, a first output signal. According to the first output signal, the operating circuit generates a second output signal at a first voltage level in a first period and a second output at a second voltage level in a second period. According to the second output signal, a pixel circuit glows. The first period and the second period are arranged in sequence.

Description

Temperature sensing device and temperature sensing method

The present disclosure relates to a sensing technology, and more particularly to a temperature sensing device and a temperature sensing method.

Each thin-film transistor (TFT) in the circuit experiences variations in the output signal to the compensation integrated circuit (IC) due to threshold voltage (VTH) fluctuations. Therefore, designing solutions to these problems is a key issue in this field.

A temperature sensing device includes a temperature sensing circuit that generates a first output signal in response to a current signal; and an operation circuit that generates a second output signal based on a first voltage level of the first output signal during a first time interval and a second voltage level of the first output signal during a second time interval. A pixel circuit emits light based on the second output signal, and the first and second time intervals are sequentially arranged.

In some embodiments, a temperature sensing circuit includes a current source, a first switch, and a second switch. The current source generates a current signal; a first terminal of the first switch is coupled to the current source to receive the current signal; and a first terminal of the second switch is coupled to a control terminal of the first switch, and a second terminal of the second switch outputs a first output signal.

In some embodiments, the second switch is turned on during the first time period and the second time period to output the first output signal.

In some embodiments, the temperature sensing circuit senses an ambient temperature during a first time period and a second time period to generate a first output signal.

In some embodiments, the computing circuit includes a subtractor that computes the difference between the first voltage level and the second voltage level to generate a third output signal.

In some embodiments, the operational circuit further includes a temperature compensation control circuit that generates a second output signal in response to the third output signal.

In some embodiments, the pixel circuit includes a light-emitting element, a first switch, a second switch, and a capacitor. A first terminal of the first switch receives a second output signal; a first terminal of the second switch is coupled to the first terminal of the light-emitting element, a second terminal of the second switch is coupled to a voltage source, and a control terminal of the second switch is coupled to the second terminal of the first switch; and a first terminal of the capacitor is coupled between the second terminal of the first switch and the control terminal of the second switch, and a second terminal of the capacitor is coupled between the voltage source and the second terminal of the second switch.

A temperature sensing method includes generating a current signal having a first current level during a first time period using a current source; generating a current signal having a second current level during a second time period using the current source; calculating a difference between a first voltage level corresponding to the first current level and a second voltage level corresponding to the second current level using a subtractor to generate a first output signal; detecting the first output signal to generate a second output signal using a temperature compensation control circuit; and adjusting the brightness of a pixel circuit in response to the second output signal.

In some embodiments, calculating the difference between the first voltage level and the second voltage level by a subtractor to generate a first output signal includes: receiving and temporarily storing the first voltage level in the subtractor during a first time period by the subtractor.

In some embodiments, calculating the difference between the first voltage level and the second voltage level by the subtractor to generate the first output signal includes calculating the difference between the second voltage level and the first voltage level by the subtractor during the second time period.

The following disclosure provides numerous different embodiments or examples for implementing various features of this disclosure. Components and configurations from specific examples are used in the following discussion to simplify the disclosure. Any examples discussed are for illustrative purposes only and are not intended to limit the scope or meaning of this disclosure or its examples in any way. Where appropriate, identical reference numbers are used throughout the drawings and accompanying text to represent identical or similar elements.

FIG1 is a schematic diagram of a display device 10 according to some embodiments of the present disclosure.

The display device 10 in FIG. 1 includes a plurality of pixel cells 15 arranged in an array. Each pixel cell 15 includes a sensor 20 and a pixel circuit 40. The sensor 20 detects changes in ambient temperature and adjusts the brightness of the pixel circuit 40 accordingly. Details of the sensor 20 and pixel circuit 40 are further described in the following embodiments shown in FIG. 2 through FIG. 5.

FIG2 is a schematic diagram of a display device 10 according to some embodiments of the present disclosure. Referring to FIG1 and FIG2 , the display device 10 shown in FIG2 is a variation of the display device 10 shown in FIG1 . Compared to the pixel unit 15 in FIG1 , the pixel unit 15 in FIG2 includes a sensor 20 and eight pixel circuits 40 . The brightness of the eight pixel circuits 40 is adjusted by a common sensor 20 and surrounds the shared sensor 20.

In various embodiments, the number of sensors 20 and pixel circuits 40 in the pixel unit 15 can be adjusted according to actual needs and is not limited to the numbers shown in Figures 1 and 2.

Figures 3 to 5 illustrate the circuit structures of sensor 20 and pixel circuit 40. First, the sensor 20 is described, followed by the pixel circuit 40.

Please refer to FIG. 3 , which is a schematic diagram of a temperature sensing circuit 25 according to some embodiments of the present disclosure. Referring to FIG. 1 through FIG. 3 , the temperature sensing circuit 25 may be included in the sensor 20 . As shown in FIG. 3 , the temperature sensing circuit 25 includes a current source 110 and switches T1 and T2 . In some embodiments, switches T1 and T2 may be implemented using transistors.

In some embodiments, a current source 110 is configured to generate a current signal IB. A first terminal of a switch T1 is coupled to the current source 110 to receive the current signal IB, and a second terminal of the switch T1 is configured to receive a reference voltage signal VSS. In some embodiments, the reference voltage signal VSS has a ground voltage level. A first terminal of a switch T2 is coupled to a control terminal of the switch T1. The switch T1 is configured to sense an ambient temperature. Based on the ambient temperature sensed by the switch T1, the switch T2 outputs an output signal VO at a second terminal of the switch T2, and the control terminal of the switch T2 is configured to receive the voltage signal GT1.

In some embodiments, current source 110 is configured to generate a current signal IB having different current levels in different sensing regions. The output signal VDIO between the first terminal of switch T2 and the control terminal of switch T1 is determined by the current level of current signal IB. For example, as the current level of current signal IB increases, the voltage level of output signal VDIO also increases.

For example, the timing diagram shown in Figure 6 has two sensing intervals, P1 and P2. Current signal IB has current levels I1 and I2 during sensing intervals P1 and P2, respectively. Output signal VO has voltage levels VO(P1) and VO(P2) during sensing intervals P1 and P2, respectively. Simultaneously, the control terminal of switch T2 turns on in response to voltage signal GT1, outputting signal VO.

The voltage level VO(P1) and the voltage level VO(P2) can be described by the following formula (1) and formula (2) respectively: VO(P1) = Formula (1); VO(P2) = Formula (2); where Kn is the gain factor of switch T1 and VTH is the threshold voltage of switch T1. The output signal VO can reflect the external ambient temperature factor. The gain factor Kn is a temperature-dependent variable and has a positive relationship with temperature changes. For example, when the ambient temperature increases, the gain factor Kn increases.

The output signal VO generated by the temperature sensing circuit 25 is then processed by the calculation circuit 30. The processing process will be explained below with reference to FIG. 4.

Please refer to FIG. 4 . FIG. 4 is a schematic diagram of an operational circuit 30 according to some embodiments of the present disclosure. The operational circuit 30 may be included in the sensor 20 . As shown in FIG. 3 , the operational circuit 30 includes a subtractor 120 and a temperature compensation control circuit 130 .

The subtractor 120 receives an output signal VO having a voltage level VO(P1) and an output signal VO having a voltage level VO(P2) to generate an output signal VOUT. In some embodiments, the subtractor 120 calculates the difference between the voltage levels VO(P1) and VO(P2) to generate the output signal VOUT.

The voltage level VOUTL of the output signal VOUT can be described by the following formula (3): VOUTL=VO(P2) — VO(P1)= Formula (3) From Formula (3), it can be seen that the output signal VOUT is not affected by the threshold voltage VTH of switch T1. On the other hand, the output signal VOUT is affected by the gain factor Kn to reflect the ambient temperature.

Then, the temperature compensation control circuit 130 generates an output signal VFB reflecting the ambient temperature in response to the output signal VOUT, and feeds the output signal VFB back to the pixel circuit 40 to adjust the brightness of the pixel circuit 40.

In some methods, the output signal is not processed in a manner similar to formula (3), so the output signal is affected by the threshold voltage VTH of each switch.

In some other methods, a differential circuit is introduced to solve the problems of the aforementioned methods, which results in an increase in the circuit area.

In the disclosed embodiment, a calibrated output signal is generated by using different currents in two sensing regions through the current source 110. This not only corrects for variations in the threshold voltage VTH due to process offsets, but also reduces the circuit area occupied.

Please refer to FIG5 , which is a schematic diagram of a pixel circuit 40 according to some embodiments of the present disclosure. The pixel circuit 40 may correspond to the pixel circuit 40 in FIG1 and FIG2 .

The pixel circuit 40 includes switches T3 and T4, a capacitor C, and a light-emitting element 140. In some embodiments, switches T3 and T4 can be implemented by transistors. In some embodiments, the light-emitting element 140 can be implemented by a light-emitting diode.

The first terminal of the light-emitting element 140 is configured to receive a reference voltage signal VSS. In some embodiments, the reference voltage signal VSS is at a ground voltage level. The first terminal of the switch T3 receives the output signal VFB, and the control terminal of the switch T3 receives the voltage signal GT2. The first terminal of the switch T4 is coupled to the second terminal of the light-emitting element 140, the second terminal of the switch T4 is coupled to the voltage source VDD, and the control terminal of the switch T4 is coupled to the second terminal of the switch T3. The first terminal of the capacitor C is coupled to the second terminal of the switch T3, and the second terminal of the capacitor C is coupled to the voltage source VDD.

Switch T3 turns on in response to voltage signal GT2, transmitting output signal VFB to node N1. Capacitor C charges in response to output signal VFB. When switch T3 turns on, switch T4 turns on in response to output signal VFB being transmitted to node N1.

Then, switch T3 turns off in response to voltage signal GT2. Capacitor C discharges through switch T4 to adjust the voltage level of node N1. Correspondingly, the current level of the current signal passing through switch T4 changes, adjusting the brightness of light-emitting element 140.

FIG6 is a timing diagram of the light emitting operation of the pixel unit 15 according to some embodiments of the present disclosure. For easier understanding, the description of FIG6 should be used in conjunction with FIG3 to FIG5.

FIG. 6 shows the current signal IB, output signals VDIO and VO of the temperature sensing circuit 25, the voltage signal GT1 received by the control end of the switch T2, the output signal VOUT of the calculation circuit 30, and the voltage signal GT2 received by the control end of the switch T3 of the pixel circuit 40.

The timing diagram shown in FIG6 includes intervals F1 and F2. During interval F1, display device 10 displays the Nth frame of image, and during interval F2, display device 10 displays the N+1th frame of image. Interval F1 includes sequentially arranged sensing intervals P1 and P2, writing interval P3, and driving interval P4. Interval F2 includes sequentially arranged sensing intervals P5 and P6, writing interval P7, and driving interval P8.

During sensing interval P1, current signal IB has a current level I1. In some embodiments, the current level I1 may be 0.5 microamperes (μA), and the length of sensing interval P1 may be 16.6 microseconds (μs).

During sensing period P1, the voltage level of voltage signal GT1 rises from voltage level VGL to voltage level VGH. The voltage level of output signal VDIO increases in response to the increase in current level I1. The voltage level of output signal VO is raised to the voltage level of output signal VDIO. Switch T2 generates output signal VO based on the ambient temperature sensed by switch T1. The specific relationship between output signal VO and temperature can be found in the aforementioned formula (2).

During the sensing period P1, both the output signal VDIO and the output signal VO rise from the initial voltage level V0 to the voltage level VO(P1). In some embodiments, the value of the voltage level VO(P1) can be 1.665 volts (V).

In the next sensing interval P2, the current signal IB has a current level I2, which is greater than the current level I1. In some embodiments, the value of the current level I2 may be 10 microamperes (μA), and the length of the sensing interval P2 may be 16.6 microseconds (μs).

During sensing period P2, the voltage level of voltage signal GT1 remains at voltage level VGH, while the voltage level of output signal VDIO increases in response to current level I2. The voltage level of output signal VO is increased to the voltage level of output signal VDIO.

Both output signals VDIO and VO rise to voltage level VO(P2) during sensing period P2. Switch T2 generates output signal VO based on the ambient temperature sensed by switch T1. In some embodiments, voltage level VO(P2) can be 2.414 volts (V).

In some embodiments, during the sensing period P1, the subtractor 120 receives the output signal VO having the voltage level VO(P1) and temporarily stores the voltage level VO(P1) inside the subtractor 120.

During sensing period P2, subtractor 120 receives output signal VO having voltage level VO(P2). Subtractor 120 calculates the difference between voltage levels VO(P1) and VO(P2). In some embodiments, the difference in voltage levels is 0.749 volts (V).

After the sensing operations in the P1 and P2 are completed, the writing operation in the P3 is performed.

During write period P3, output signals VDIO, VO, and VOUT drop to initial voltage level V0, current signal IB drops to initial current level I0, and voltage signal GT1 changes from voltage level VGH to voltage level VGL. In some embodiments, voltage level VGH is greater than voltage level VGL.

During the write period P3, the control terminal of the switch T3 is turned on in response to the voltage signal GT2 having the voltage level VGH. The capacitor C is charged in response to the output signal VFB (not shown in FIG6 ), and the switch T4 is turned on in response to the output signal VFB.

The voltage level of the output signal VFB generated by the temperature compensation control circuit 130 during the operation in the sections P1 to P3 corresponds to the ambient temperature in the sensing sections P1 and P2.

After writing to interval P3, the operation of driving interval P4 is carried out.

During the driving period P4, the voltage level of the voltage signal GT2 received by the control terminal of the switch T3 of the pixel circuit 40 changes from the voltage level VGH to the voltage level VGL. At this time, the capacitor C of the pixel circuit 40 discharges to adjust the brightness of the light-emitting element 140.

At the beginning of the sensing period P5, the current signal IB changes from the current level I0 to the current level I1.

During sensing period P5, the voltage level of voltage signal GT1 rises from voltage level VGL to voltage level VGH. In response to the increase in current level I1, the voltage level of output signal VDIO is increased. The voltage level of output signal VO is also increased to the voltage level of output signal VDIO.

During sensing region P5, both output signal VDIO and output signal VO increase from initial voltage level V0 to voltage level VO(P5). In some embodiments, the difference between voltage level VO(P5) and voltage level VO(P1) is related to the difference between the ambient temperature of sensing region P5 and the ambient temperature of sensing region P1.

For example, when the ambient temperature of the sensing section P5 is the same as the ambient temperature of the sensing section P1, the voltage level VO(P5) is equal to the voltage level VO(P1).

When the ambient temperature of the sensing section P5 is greater than the ambient temperature of the sensing section P1, the voltage level VO(P5) is less than the voltage level VO(P1); and when the ambient temperature of the sensing section P5 is less than the ambient temperature of the sensing section P1, the voltage level VO(P5) is greater than the voltage level VO(P1).

At the beginning of the sensing period P6, the current signal IB changes from the current level I1 to the current level I2.

During sensing period P6, the voltage level of voltage signal GT1 remains at voltage level VGH, while the voltage level of output signal VDIO increases in response to current level I2. The voltage level of output signal VO is increased to the voltage level of output signal VDIO.

Both output signal VDIO and output signal VO rise to voltage level VO(P6) during sensing period P6. In some embodiments, the difference between voltage level VO(P6) and voltage level VO(P2) is similar to the difference between voltage level VO(P5) and voltage level VO(P1) described above, and therefore will not be repeated here.

Both output signal VDIO and output signal VO rise to voltage level VO(P6) during sensing period P6. In some embodiments, the difference between voltage level VO(P6) and voltage level VO(P2) is similar to the difference between voltage level VO(P5) and voltage level VO(P1) described above, and therefore will not be repeated here.

The voltage level of the output signal VFB generated by the output signal VOUT is reflected in the ambient temperature of the sensing areas P5 and P6.

The process of writing to interval P7 and driving interval P8 is similar to that of writing to interval P3 and driving interval P4, so it will not be repeated here.

In summary, the temperature sensing device disclosed herein generates output signals with varying voltage levels at different time intervals and uses these output signals to correct for process-induced drift in the transistor's threshold voltage. This design not only resolves the aforementioned issues but also significantly reduces the circuit footprint compared to designs using differential circuits.

The foregoing content summarizes the features of several embodiments so that those skilled in the art can better understand the aspects of one embodiment of the present disclosure. Those skilled in the art should understand that they can easily use one embodiment of the present disclosure as a basis for designing or modifying other processes and structures for performing the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also appreciate that such equivalent structures do not depart from the spirit and scope of one embodiment of the present disclosure, and that those skilled in the art can make various changes, substitutions, and modifications herein without departing from the spirit and scope of one embodiment of the present disclosure.

10: Display device 15: Pixel unit 20: Sensor 25: Temperature sensing circuit 30: Calculation circuit 40: Pixel circuit 110: Current source 120: Subtractor 130: Temperature compensation control circuit 140: Light-emitting element C: Capacitor GT1, GT2: Voltage signal I0: Initial current level IB: Current signal I1, I2: Current level N1: Node P1, P2, P5, P6: Sensing region P3, P7: Writing region P4, P8: Driving region T1, T2, T3, T4: Switches F1, F2: Regions N, N+1: Frames V0: Initial voltage level VDD: Voltage Source VDIO, VFB, VO, VOUT: Output Signals VGH, VGL, VO(P1), VO(P2), VO(P5), VO(P6), VOUTL: Voltage Levels VSS: Voltage Signal

Various aspects of one embodiment of the present disclosure are best understood from the following detailed description in conjunction with the accompanying drawings. Note that, in accordance with standard industry practice, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion. Figure 1 is a system schematic diagram of a display device according to some embodiments of the present disclosure. Figure 2 is a system schematic diagram of a display device according to other embodiments of the present disclosure. Figure 3 is a schematic diagram of a temperature sensing circuit according to some embodiments of the present disclosure. Figure 4 is a schematic diagram of an operational circuit according to some embodiments of the present disclosure. Figure 5 is a schematic diagram of a pixel circuit according to some embodiments of the present disclosure. Figure 6 is a schematic diagram of a pixel unit driving waveform according to some embodiments of the present disclosure.

Domestic Storage Information (Please enter in order by institution, date, and number) None International Storage Information (Please enter in order by country, institution, date, and number) None

25: Temperature sensing circuit

110: Current Source

GT1: Voltage signal

IB: Current signal

T1, T2: switch

VDIO, VO: output signal

VSS: voltage signal

Claims (9)

A temperature sensing device comprises: a temperature sensing circuit for generating a first output signal in response to a current signal; and an operating circuit for generating a second output signal based on a first voltage level of the first output signal during a first time period and a second voltage level of the first output signal during a second time period, wherein the temperature sensing circuit comprises: a current source for generating the current signal; a first switch, having a drain terminal and a gate terminal coupled to the current source to receive the current signal, and a source terminal of the first switch coupled to a reference voltage to receive a reference voltage signal; and A second switch, a drain terminal of the second switch coupled to the gate terminal of the first switch and the current source, a source terminal of the second switch configured to output the first output signal; a pixel circuit configured to emit light in response to the second output signal; and the first time period and the second time period are sequentially arranged. The temperature sensing device as described in claim 1, wherein the second switch is turned on during the first time period and the second time period to output the first output signal. The temperature sensing device as described in claim 2, wherein the temperature sensing circuit is used to sense an ambient temperature during the first time period and the second time period to generate the first output signal. The temperature sensing device as described in claim 1, wherein the operating circuit includes a subtractor for calculating a difference between the first voltage level and the second voltage level to generate a third output signal. The temperature sensing device of claim 4, wherein the operational circuit further comprises a temperature compensation control circuit for generating the second output signal in response to the third output signal. The temperature sensing device of claim 1, wherein the pixel circuit comprises: a light-emitting element; a third switch, a first terminal of the third switch for receiving the second output signal; a fourth switch, a first terminal of the fourth switch coupled to a first terminal of the light-emitting element, a second terminal of the fourth switch coupled to a voltage source, and a control terminal of the fourth switch coupled to a second terminal of the third switch; and a capacitor, a first terminal of the capacitor coupled between the second terminal of the third switch and the control terminal of the fourth switch, and a second terminal of the capacitor coupled between the voltage source and the second terminal of the fourth switch. A temperature sensing method includes: Generating a current signal having a first current level during a first time period by a current source in a temperature sensing circuit, wherein the temperature sensing circuit includes: A current source for generating the current signal; A first switch, having a drain and a gate coupled to the current source to receive the current signal, and a source coupled to a reference voltage to receive a reference voltage signal; and A second switch, having a drain coupled to the gate of the first switch and the current source, and a source for outputting a first output signal; Generating the current signal having a second current level during a second time period by the current source; A subtractor calculates a difference between a first voltage level corresponding to the first current level and a second voltage level corresponding to the second current level to generate the first output signal. A temperature compensation control circuit detects the first output signal to generate a second output signal. The brightness of a pixel circuit is adjusted in response to the second output signal. The temperature sensing method of claim 7, wherein calculating the difference between the first voltage level and the second voltage level by the subtractor to generate the first output signal comprises: Receiving and temporarily storing the first voltage level in the subtractor during the first time period by the subtractor. The temperature sensing method of claim 8, wherein calculating the difference between the first voltage level and the second voltage level by the subtractor to generate the first output signal comprises: Calculating the difference between the second voltage level and the first voltage level by the subtractor during the second time period.