Light sensing circuit and display device

Abstract

The utility model provides a light sensing circuit and a display device. The light sensing circuit comprises a light sensing element, a first processing circuit and a second processing circuit; the first processing circuit comprises a first operational amplifier and a first resistor; the photosensitive element is electrically connected with the reverse input end of the first operational amplifier and is used for converting a received optical signal into a light current signal and providing the light current signal to the reverse input end of the first operational amplifier; the first end of the first resistor is electrically connected with the reverse input end of the first operational amplifier, and the second end of the first resistor is electrically connected with the output end of the first operational amplifier; and the second processing circuit is used for performing phase reversal processing on the output voltage provided by the output end of the first operational amplifier to obtain a photovoltage signal. According to the utility model, the leakage current of the photosensitive element is not reduced, so that the voltage value of the photovoltage signal obtained according to the leakage current can meet the voltage acquisition range of a rear-end analog-to-digital conversion module.

Description

Technical Field

[0001] The utility model relates to the field of display technology, and in particular to a light sensing circuit and a display device. Background Art

[0002] Currently, all mobile phones on the market can realize light sensing function, which automatically adjusts the brightness of the mobile phone screen according to the brightness of the surrounding light. The sensor is integrated into the whole device, converting the light signal into an electrical signal, and then adjusting the backlight current to control the brightness of the mobile phone screen. In the field of LCD (liquid crystal display) display, for LTPS (low-temperature polycrystalline silicon) display products, since the top gate structure cannot transmit light, a new process design is required to achieve the light sensing function. However, the problem with LTPS display products is that the internal resistance of the light-sensitive TFT (thin-film transistor) is small, and the leakage current of the light-sensitive TFT will be greatly reduced after the external pull-down resistor is connected. Summary of the Invention

[0003] The main purpose of the utility model is to provide a light-sensing circuit and a display device, which solve the problem that the leakage current of the light-sensing TFT is reduced after the light-sensing TFT is externally connected to a pull-down resistor.

[0004] In one aspect, an embodiment of the present invention provides a light sensing circuit, comprising a light sensing element, a first processing circuit, and a second processing circuit;

[0005] The first processing circuit includes a first operational amplifier and a first resistor;

[0006] The photosensitive element is electrically connected to the reverse input terminal of the first operational amplifier, and is used to convert the received light signal into a photocurrent signal, and provide the photocurrent signal to the reverse input terminal of the first operational amplifier; the positive input terminal of the first operational amplifier is electrically connected to the first DC voltage terminal;

[0007] A first end of the first resistor is electrically connected to an inverting input terminal of the first operational amplifier, and a second end of the first resistor is electrically connected to an output terminal of the first operational amplifier;

[0008] The second processing circuit is electrically connected to the output terminal of the first operational amplifier and the photovoltage output terminal, and is used to invert the output voltage provided by the output terminal of the first operational amplifier to obtain and provide a photovoltage signal through the photovoltage output terminal.

[0009] Optionally, the second processing circuit includes a second operational amplifier, a second resistor and a third resistor;

[0010] A first end of the second resistor is electrically connected to the output end of the first operational amplifier, and a second end of the second resistor is electrically connected to the inverting input end of the second operational amplifier;

[0011] The first end of the third resistor is electrically connected to the second end of the second resistor, and the second end of the third resistor is electrically connected to the output end of the second operational amplifier;

[0012] The positive input terminal of the second operational amplifier is electrically connected to the second DC voltage terminal; the output terminal of the second operational amplifier is electrically connected to the photovoltage output terminal.

[0013] Optionally, the first processing circuit further includes a first capacitor;

[0014] The first end of the first capacitor is electrically connected to the first end of the first resistor, and the second end of the first capacitor is electrically connected to the second end of the first resistor.

[0015] Optionally, the second processing circuit further includes a second capacitor;

[0016] The first end of the second capacitor is electrically connected to the first end of the third resistor, and the second end of the second capacitor is electrically connected to the second end of the third resistor.

[0017] Optionally, both the first DC voltage terminal and the second DC voltage terminal are ground terminals.

[0018] Optionally, the photosensitive element is a photosensitive transistor;

[0019] The gate of the photosensitive transistor is electrically connected to the first voltage terminal, the first electrode of the photosensitive transistor is electrically connected to the bias voltage terminal, and the second electrode of the photosensitive transistor is electrically connected to the inverting input terminal of the first operational amplifier.

[0020] Optionally, the resistance value of the first resistor is greater than 10 MΩ.

[0021] Optionally, the resistance value of the second resistor is equal to the resistance value of the third resistor.

[0022] In a second aspect, the present invention provides a display device comprising the above-mentioned light sensing circuit.

[0023] The display device according to at least one embodiment of the present invention further includes a voltage follower and an analog-to-digital conversion module;

[0024] The photovoltage output terminal is electrically connected to the analog-to-digital conversion module through the voltage follower;

[0025] The analog-to-digital conversion module is used to perform analog-to-digital conversion on the photovoltage signal to obtain a digital photovoltage signal.

[0026] The photosensitive circuit and display device described in the embodiment of the present invention do not require a pull-down resistor to be connected in series with the internal resistance of the photosensitive element, and will not reduce the leakage current of the photosensitive element itself, so that the voltage value of the photovoltage signal obtained according to the leakage current can meet the acquisition voltage range of the back-end analog-to-digital conversion module. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a structural diagram of a light sensing circuit according to at least one embodiment of the present utility model;

[0028] Figure 2 is a circuit diagram of a light sensing circuit according to at least one embodiment of the present utility model;

[0029] Figure 3 is a circuit diagram of a light sensing circuit according to at least one embodiment of the present utility model;

[0030] Figure 4 is a circuit diagram of a light sensing circuit according to at least one embodiment of the present utility model;

[0031] Figure 5 It is a structural diagram of a display device according to at least one embodiment of the present utility model. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The transistors used in all embodiments of the present invention can be thin film transistors, field effect transistors, or other devices with the same characteristics. In the embodiments of the present invention, to distinguish the two electrodes of the transistor except the gate, one electrode is called the first electrode and the other electrode is called the second electrode.

[0034] In actual operation, when the transistor is a thin film transistor or a field effect transistor, the first electrode may be a drain electrode, and the second electrode may be a source electrode; or, the first electrode may be a source electrode, and the second electrode may be a drain electrode.

[0035] like Figure 1 As shown, the light sensing circuit according to the embodiment of the present utility model includes a light sensing element GE, a first processing circuit and a second processing circuit 12;

[0036] The first processing circuit 11 includes a first operational amplifier A1 and a first resistor R1;

[0037] The photosensitive element GE is electrically connected to the inverting input terminal of the first operational amplifier A1, and is used to convert the received light signal into a photocurrent signal Iph, and provide the photocurrent signal Iph to the inverting input terminal of the first operational amplifier A1; the positive input terminal of the first operational amplifier A1 is electrically connected to the first DC voltage terminal VZ1;

[0038] A first end of the first resistor R1 is electrically connected to the inverting input terminal of the first operational amplifier A1, and a second end of the first resistor R1 is electrically connected to the output terminal of the first operational amplifier A1;

[0039] The second processing circuit 12 is electrically connected to the output terminal of the first operational amplifier A1 and the photovoltage output terminal GT, and is used to invert the output voltage provided by the output terminal of the first operational amplifier A1 to obtain and provide a photovoltage signal through the photovoltage output terminal GT.

[0040] In at least one embodiment of the present invention, the second processing circuit 12 inverting the output voltage may refer to:

[0041] inverting the output voltage; or,

[0042] The output voltage is inverted, and a ratio between an absolute value of a voltage value of the inverted output voltage and an absolute value of a voltage value of the output voltage is A, where A is greater than 1, or A is greater than 0 and less than 1.

[0043] In the photosensor circuit described in the embodiment of the present invention, the photocurrent Iph does not pass through a pull-down resistor but is directly electrically connected to the inverting input terminal of the first operational amplifier A1. After Iph passes through R1, the output voltage provided by the output terminal of the first operational amplifier A1 has a voltage value equal to Iph × R1z, where R1z is the resistance value of R1. The second processing circuit 12 inverts the output voltage to obtain and provide a photovoltage signal through the photovoltage output terminal GT. The photosensor circuit described in the present invention does not require a pull-down resistor connected in series with the internal resistance of the photosensitive element GE, and does not reduce the leakage current of the photosensitive element GE itself. Consequently, the voltage value of the photovoltage signal obtained based on this leakage current can meet the acquisition voltage range of the back-end analog-to-digital conversion module.

[0044] In at least one embodiment of the present invention, the second processing circuit includes a second operational amplifier, a second resistor, and a third resistor;

[0045] A first end of the second resistor is electrically connected to the output end of the first operational amplifier, and a second end of the second resistor is electrically connected to the inverting input end of the second operational amplifier;

[0046] The first end of the third resistor is electrically connected to the second end of the second resistor, and the second end of the third resistor is electrically connected to the output end of the second operational amplifier;

[0047] The positive input terminal of the second operational amplifier is electrically connected to the second DC voltage terminal; the output terminal of the second operational amplifier is electrically connected to the photovoltage output terminal.

[0048] In a specific implementation, the second processing circuit may include a second operational amplifier, a second resistor and a third resistor; the second resistor is arranged between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier, and the third resistor is arranged between the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier. The second operational amplifier is used to invert the output voltage provided by the first operational amplifier to obtain and provide a photovoltage signal through the photovoltage output terminal GT.

[0049] like Figure 2 As shown, in Figure 1 Based on at least one embodiment of the light sensing circuit shown, the second processing circuit includes a second operational amplifier A2, a second resistor R2, and a third resistor R3;

[0050] A first end of the second resistor R2 is electrically connected to the output end of the first operational amplifier A1, and a second end of the second resistor R2 is electrically connected to the inverting input end of the second operational amplifier A2;

[0051] The first end of the third resistor R3 is electrically connected to the second end of the second resistor R2, and the second end of the third resistor R3 is electrically connected to the output end of the second operational amplifier A2;

[0052] The positive input terminal of the second operational amplifier A2 is electrically connected to the second DC voltage terminal VZ2; the output terminal of the second operational amplifier A2 is electrically connected to the photovoltage output terminal GT.

[0053] Optionally, the first DC voltage terminal and the second DC voltage terminal may both be ground terminals.

[0054] Optionally, the first processing circuit further includes a first capacitor;

[0055] The first end of the first capacitor is electrically connected to the first end of the first resistor, and the second end of the first capacitor is electrically connected to the second end of the first resistor.

[0056] Optionally, the second processing circuit further includes a second capacitor;

[0057] The first end of the second capacitor is electrically connected to the first end of the third resistor, and the second end of the second capacitor is electrically connected to the second end of the third resistor.

[0058] like Figure 3 As shown, in Figure 2 Based on at least one embodiment of the light sensing circuit shown, the first processing circuit may further include a first capacitor C1, and the second processing circuit may include a second capacitor C2;

[0059] A first end of C1 is electrically connected to a first end of R1, and a second end of C1 is electrically connected to a second end of R1;

[0060] A first end of C2 is electrically connected to a first end of R3, and a second end of C2 is electrically connected to a second end of R3;

[0061] The first DC voltage terminal and the second DC voltage terminal are both ground terminals GND.

[0062] Optionally, the photosensitive element is a photosensitive transistor;

[0063] The gate of the photosensitive transistor is electrically connected to the first voltage terminal, the first electrode of the photosensitive transistor is electrically connected to the bias voltage terminal, and the second electrode of the photosensitive transistor is electrically connected to the inverting input terminal of the first operational amplifier.

[0064] In a specific implementation, the photosensitive element may be a photosensitive transistor, which is used to convert the received light signal into a photocurrent signal and provide the photocurrent signal to the inverting input terminal of the first operational amplifier.

[0065] Optionally, when the photosensitive transistor is an n-type transistor, the first voltage end may be a low voltage end; when the photosensitive transistor is a p-type transistor, the first voltage end may be a high voltage end; so that the photosensitive transistor is in a cut-off region, enabling the photosensitive transistor to perform photoelectric conversion.

[0066] Optionally, the resistance value of the first resistor is greater than 10 MΩ.

[0067] In at least one embodiment of the present invention, the resistance value of the second resistor is equal to the resistance value of the third resistor, but the present invention is not limited thereto.

[0068] In a specific implementation, the resistance value of the second resistor and the resistance value of the third resistor can be set as needed. The resistance value of the third resistor can also be greater than the resistance value of the second resistor, or the resistance value of the third resistor can be less than the resistance value of the second resistor.

[0069] like Figure 4 As shown, in Figure 3 Based on at least one embodiment of the light sensing circuit shown, the light sensing element is a light sensing transistor T0;

[0070] The gate of the photosensitive transistor T0 is electrically connected to the low voltage terminal VGL, the first electrode of the photosensitive transistor T0 is electrically connected to the bias voltage terminal VB, and the second electrode of the photosensitive transistor is electrically connected to the inverting input terminal of the first operational amplifier A1; the bias voltage terminal VB is used to provide a bias voltage Vbias;

[0071] The resistance value R1z of R1 may be 100 MΩ, and the resistance values ​​R2z of R2 and R3z of R3 may be 1 KΩ.

[0072] exist Figure 4 In at least one embodiment shown, T0 is an n-type transistor, the gate of T0 is electrically connected to the low voltage terminal VGL, and the voltage value Vgl of the low voltage signal provided by the low voltage terminal VGL can be a negative value, so that T0 is in the cut-off region and T0 can perform photoelectric conversion.

[0073] Figure 4 When at least one embodiment of the photosensor circuit shown is in operation, T0 converts the received light signal into a photocurrent signal Iph. The photocurrent signal Iph can be the leakage current of T0. The photocurrent signal Iph does not pass through the pull-down resistor and is directly connected to the reverse input terminal of A1. The output voltage Vout1 provided by the output terminal of A1 is equal to -Iph×R1z. The output terminal of A1 is electrically connected to the reverse input terminal of A2 through R2. The voltage value Vout2 of the photovoltage signal provided by GT is equal to (R3z / R2z)×(Iph×R1z). Vout2 is transmitted to the ADC module (analog-to-digital conversion module) through the voltage follower. Figure 4 At least one embodiment of the photosensor circuit shown can convert a photocurrent signal into a photovoltage signal and transmit the photovoltage signal to the ADC module without directly connecting a pull-down resistor and the internal resistance of the photosensitive transistor in series, and will not reduce the leakage current of the photosensitive transistor itself, so that the voltage value of the photovoltage signal can meet the acquisition voltage range of the ADC module.

[0074] Optionally, the acquisition voltage range of the ADC module may be greater than or equal to 0.55V and less than or equal to 4.15V.

[0075] In at least one embodiment of the present invention, R2z may be smaller than R3z, or R2z may be larger than R3z.

[0076] The display device described in the embodiment of the present invention includes the above-mentioned light sensing circuit.

[0077] The display device according to at least one embodiment of the present invention further includes a voltage follower and an analog-to-digital conversion module;

[0078] The photovoltage output terminal is electrically connected to the analog-to-digital conversion module through the voltage follower;

[0079] The analog-to-digital conversion module is used to perform analog-to-digital conversion on the photovoltage signal to obtain a digital photovoltage signal.

[0080] like Figure 5 As shown, the display device according to at least one embodiment of the present invention may include a light sensing circuit 50, a voltage follower 51 and an analog-to-digital conversion module 52;

[0081] The light sensing circuit 50 includes a photovoltage output terminal GT, which is used to provide a photovoltage signal through the photovoltage output terminal GT;

[0082] The photovoltage output terminal GT is electrically connected to the analog-to-digital conversion module 52 through the voltage follower 51;

[0083] The analog-to-digital conversion module 52 is used to perform analog-to-digital conversion on the photovoltage signal to obtain a digital photovoltage signal.

[0084] After actual testing, when the illumination of the light signal received by the photosensitive element changes from 0 lux to 600 lux, the change difference of the voltage value of the photovoltage signal is approximately 976 mV;

[0085] When the illumination of the light signal is 0 lux, the voltage value of the photovoltage signal is 2583 mV;

[0086] When the illumination of the optical signal is 600 lux, the voltage value of the photovoltage signal is 3560 mV;

[0087] Therefore, the illumination of the corresponding light signal can be calculated according to the voltage value of the photovoltage signal.

[0088] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles described in the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A light sensing circuit, characterized in that: comprising a photosensitive element, a first processing circuit and a second processing circuit; The first processing circuit includes a first operational amplifier and a first resistor; The photosensitive element is electrically connected to the reverse input terminal of the first operational amplifier, and is used to convert the received light signal into a photocurrent signal, and provide the photocurrent signal to the reverse input terminal of the first operational amplifier; the positive input terminal of the first operational amplifier is electrically connected to the first DC voltage terminal; A first end of the first resistor is electrically connected to an inverting input terminal of the first operational amplifier, and a second end of the first resistor is electrically connected to an output terminal of the first operational amplifier; The second processing circuit is electrically connected to the output terminal of the first operational amplifier and the photovoltage output terminal, and is used to invert the output voltage provided by the output terminal of the first operational amplifier to obtain and provide a photovoltage signal through the photovoltage output terminal.

2. The light sensing circuit according to claim 1, wherein: The second processing circuit includes a second operational amplifier, a second resistor and a third resistor; A first end of the second resistor is electrically connected to the output end of the first operational amplifier, and a second end of the second resistor is electrically connected to the inverting input end of the second operational amplifier; The first end of the third resistor is electrically connected to the second end of the second resistor, and the second end of the third resistor is electrically connected to the output end of the second operational amplifier; The positive input terminal of the second operational amplifier is electrically connected to the second DC voltage terminal; the output terminal of the second operational amplifier is electrically connected to the photovoltage output terminal.

3. The light sensing circuit according to claim 1, wherein: The first processing circuit further includes a first capacitor; The first end of the first capacitor is electrically connected to the first end of the first resistor, and the second end of the first capacitor is electrically connected to the second end of the first resistor.

4. The light sensing circuit according to claim 2, wherein: The second processing circuit further includes a second capacitor; The first end of the second capacitor is electrically connected to the first end of the third resistor, and the second end of the second capacitor is electrically connected to the second end of the third resistor.

5. The light sensing circuit according to claim 2, wherein: The first DC voltage terminal and the second DC voltage terminal are both ground terminals.

6. The light sensing circuit according to any one of claims 1 to 5, wherein: The photosensitive element is a photosensitive transistor; The gate of the photosensitive transistor is electrically connected to the first voltage terminal, the first electrode of the photosensitive transistor is electrically connected to the bias voltage terminal, and the second electrode of the photosensitive transistor is electrically connected to the inverting input terminal of the first operational amplifier.

7. The light sensing circuit according to claim 1, wherein: The resistance value of the first resistor is greater than 10 MΩ.

8. The light sensing circuit according to claim 2, wherein: The resistance value of the second resistor is equal to the resistance value of the third resistor.

9. A display device, characterized in that: The method comprises the light sensing circuit according to any one of claims 1 to 8.

10. The display device according to claim 9, wherein It also includes a voltage follower and an analog-to-digital conversion module; The photovoltage output terminal is electrically connected to the analog-to-digital conversion module through the voltage follower; The analog-to-digital conversion module is used to perform analog-to-digital conversion on the photovoltage signal to obtain a digital photovoltage signal.

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