TWI727325B - Optical sensing device - Google Patents

Abstract

An optical sensing device is provided. The device includes a detection circuit, a conversion circuit, a coupling mode selection circuit, and an amplifying circuit. The detection circuit detects light to generate a current signal according to an intensity of light. The conversion circuit converts the current signal into a voltage signal, wherein the voltage signal includes an AC component and a DC component. The coupling mode selection circuit filters out the DC component to output the AC component or the coupling mode selection circuit does not filter out the DC component to output the DC component and the AC component. The amplifying circuit amplifies the voltage signal without the DC component to generate an output signal when the coupling mode selection circuit filters out the DC component, and the amplifying circuit amplifies the voltage signal with the DC component and the AC component to generate another output signal when the coupling mode selection circuit does not filter out the DC component.

Description

Light sensing device

This case relates to a light sensing device, and particularly a light sensing device with AC coupling mode and DC coupling mode.

A general light sensing device uses a light detecting element to detect ambient light and generate an electric current to achieve the purpose of light detection. However, the current generated by the light detection element is mostly too small, and the current generated by the light detection element contains too much noise. If the current generated by the light detection element is directly used for other applications, it is easy to cause errors in the light sensing device. action.

Furthermore, most of the circuit designs of light sensing devices use non-integrated independent passive components. However, the use of too many non-integrated independent passive components will increase the wiring and area of the circuit board layout and be susceptible to noise interference. Furthermore, if the light detection component is damaged and needs to be replaced with a different light detection component, for example, a different model of light detection component or a light detection component produced by a different manufacturer, the repairer needs to further adjust other passive components and For the parameter configuration of the related circuit, a set of circuit configuration needs to be adjusted correspondingly every time the light detection element is replaced, which makes maintenance difficult and lacks the flexibility of circuit design.

The invention provides a light sensing device. The light sensing device includes a sensing circuit, a conversion circuit, a coupling mode selection circuit, and an amplifying circuit. The sensing circuit detects a light, and generates a corresponding current signal according to the intensity of the light. The conversion circuit converts the current signal into a voltage signal, and the voltage signal includes an AC component and a DC component. The coupling mode selection circuit filters out the DC component in the voltage signal to output the AC component in the voltage signal, or the coupling mode selection circuit does not filter out the DC component and outputs a voltage signal including the AC component and the DC component. The amplifying circuit amplifies the voltage signal after filtering the DC component when the coupling mode selection circuit filters out the DC component to generate an output signal, and when the coupling mode selection circuit does not filter the DC component, it amplifies the voltage signal containing the AC component and the DC component. Generate another output signal.

Please refer to FIGS. 1 and 2 together. FIG. 1 is a block diagram of an embodiment of the light sensing device according to the present invention, and FIG. 2 is a circuit diagram of an implementation aspect of the light sensing device of FIG. 1. The light sensing device 1 includes a sensing circuit 11, a conversion circuit 12, a coupling mode selection circuit 13 and an amplifying circuit 14. The conversion circuit 12 is coupled between the sensing circuit 11 and the coupling mode selection circuit 13, and the coupling mode selection circuit 13 is coupled between the conversion circuit 12 and the amplifying circuit 14.

In an embodiment, the sensing circuit 11 can be implemented by a phototransistor or a photodiode. The sensing circuit 11 detects a light, and the sensing circuit 11 generates a corresponding current signal according to the intensity of the light. For example, the intensity of light is proportional to the current of the current signal. If the light is stronger, the sensing circuit 11 will generate a current signal with a larger current. If the light is weaker, the sensing circuit 11 will generate a larger current. Small current signal.

The conversion circuit 12 is coupled to the output terminal of the sensing circuit 11. The conversion circuit 12 receives the current signal generated by the sensing circuit 11, and the conversion circuit 12 converts the current signal into a voltage signal. The coupling mode selection circuit 13 is coupled to the output terminal of the conversion circuit 12. The coupling mode selection circuit 13 receives the voltage signal generated by the conversion circuit 12, and the coupling mode selection circuit 13 selectively filters out the DC component of the voltage signal to output its AC component That is, the coupling mode selection circuit 13 can switchably filter or not filter the DC component in the voltage signal. In detail, the optical sensing device 1 has an AC coupling mode and a DC coupling mode. When the optical sensing device 1 is in the AC coupling mode, the coupling mode selection circuit 13 filters out the DC component in the voltage signal and outputs its AC component to Reduce the rising slope and noise of the voltage signal, and the voltage signal after filtering the DC component is more stable, but its voltage level is lower; when the light sensing device 1 is in the DC coupling mode, the coupling mode selection circuit 13 does not filter out the voltage The DC component in the signal outputs a voltage signal including an AC component and a DC component. The voltage signal including the AC component and the DC component has a higher voltage level because it is not attenuated by the coupling mode selection circuit 13.

The amplifying circuit 14 is coupled to the output terminal of the coupling mode selection circuit 13. When the light sensing device 1 is in the AC coupling mode, the amplifying circuit 14 receives the coupling mode selection circuit 13 to filter out the DC component and the voltage signal containing the AC component. The amplifying circuit 14 Amplify the voltage signal after filtering the DC component and generate an output signal (hereinafter referred to as the first output signal). The first output signal is less susceptible to noise interference and has better stability; when the light sensing device 1 is in DC coupling mode When the amplifying circuit 14 receives the voltage signal including the AC component and the DC component, the amplifying circuit 14 amplifies the voltage signal without filtering the DC component and generates an output signal (hereinafter referred to as the second output signal). The second output signal is higher than the first output. The signal has a higher voltage level. Based on this, according to the AC coupling mode and the DC coupling mode of the light sensing device 1, the light sensing device 1 converts the light into a amplified first output signal that is less susceptible to noise interference, or converts the light into a higher voltage level. The second output signal is high. The light sensing device 1 can provide different output signals according to different application products. The light sensing device 1 has good product compatibility.

In one embodiment, the light sensing device 1 further includes a control circuit 16 coupled to the coupling mode selection circuit 13. The control circuit 16 can control the coupling mode selection circuit 13 to filter out the DC component in the voltage signal to output the AC component, or control the coupling The mode selection circuit 13 does not filter out the DC component in the voltage signal to output the DC component and the AC component. Therefore, the designer of the light sensing device 1 can set the control circuit 16 to generate the corresponding control signal according to the application of the light sensing device 1 and control the coupling mode selection circuit 13 to filter or not filter the DC component in the voltage signal accordingly. For example, if the light sensing device 1 is used in an environment with high noise, or the current signal generated by the photoelectric crystal or photodiode included in the sensing circuit 11 contains more noise, the control circuit 16 can be used The control makes the light sensing device 1 operate in AC coupling mode; if the current signal generated by the photoelectric crystal or photodiode included in the sensing circuit 11 generates a relatively small current signal or the light sensing device 1 is used in low noise In this environment, the light sensing device 1 can be operated in the DC coupling mode under the control of the control circuit 16.

In one embodiment, the conversion circuit 12 includes an operational amplifier 121 and a resistor 122. The operational amplifier 121 includes an output terminal, a positive input terminal, and a negative input terminal. The positive input terminal and the negative input terminal of the operational amplifier 121 are coupled to the sensing circuit 11. The operational amplifier 121 has a negative feedback circuit, and the resistor 122 is coupled between the output terminal of the operational amplifier 121 and the negative input terminal of the operational amplifier 121, that is, the output terminal of the operational amplifier 121 is coupled to its negative input terminal via the resistor 122 To form the aforementioned negative feedback circuit, the resistance value of the resistor 122 determines the magnification between the input signal and the output signal of the operational amplifier 121. Here, the current signal generated by the sensing circuit 11 flows through the resistor 122, the operational amplifier 121 generates the aforementioned voltage signal according to the magnification determined by the resistor 122 to convert the current signal into a voltage signal, and the output terminal of the operational amplifier 121 outputs a voltage signal.

Furthermore, the conversion circuit 12 further includes a capacitor 123 coupled between the output terminal of the operational amplifier 121 and the negative input terminal of the operational amplifier 121, and the capacitor 123 is connected in parallel with the resistor 122, and the capacitor 123 can filter high frequency noise. In one embodiment, the resistor 122 is a variable resistor whose resistance value can be adjusted. The resistance value of the resistor 122 can be controlled by the control circuit 16, and the operational amplifier 121 can generate a corresponding voltage signal according to the resistor 122 with different resistance values.

In one embodiment, the coupling mode selection circuit 13 includes an AC coupling capacitor 131 and a switch 132 (hereinafter referred to as the first switch 132). The two ends of the AC coupling capacitor 131 are respectively coupled to the output end of the operational amplifier 121 and the amplifying circuit 14, and the AC coupling capacitor 131 is connected in series to the operational amplifier 121 and the amplifying circuit 14. Two ends of the first switch 132 are also respectively coupled to the output terminal of the operational amplifier 121 and the amplifying circuit 14, and the first switch 132 is connected in parallel to the AC coupling capacitor 131. The first switch 132 is controlled by the control circuit 16 to be turned on or off, and the light sensing device 1 is switched to the DC coupling mode or the AC coupling mode by turning on or off the first switch 132.

In detail, when the first switch 132 is turned off, the AC coupling capacitor 131 filters out the DC component of the voltage signal, and the amplifying circuit 14 receives the filtered DC component through the AC coupling capacitor 131 and then the voltage signal including the AC signal is generated to generate the first Output signal; when the first switch 132 is turned on, both ends of the first switch 132 are coupled to the output terminal of the operational amplifier 121 and the amplifier circuit 14 and bypass the AC coupling capacitor 131. The AC coupling capacitor 131 is not filtered For the DC component in the voltage signal, the amplifying circuit 14 receives the voltage signal including the DC component and the AC component output by the operational amplifier 121 through the first switch 132 to generate a second output signal.

In one embodiment, the light sensing device 1 includes input and output ports P1 and P2. The input and output ports P1 and P2 are respectively located at both ends of the AC coupling capacitor 131. The output and input ports P1 and P2 can be connected to an external capacitor respectively, so that The AC coupling capacitor 131 is connected in parallel to the external capacitor, and the AC coupling capacitor 131 is connected in parallel to the external capacitor to generate a larger equivalent capacitance value, so as to further reduce the rising slope and noise of the voltage signal transmitted to the amplifying circuit 14. Based on this, through the input and output ports P1 and P2, the two ends of the AC coupling capacitor 131 can generate different equivalent capacitance values. The designer can add external capacitors to the input and output ports P1 according to the different product applications of the light sensing device 1. P2, to further enhance the product compatibility of the light sensing device 1.

In one embodiment, the coupling mode selection circuit 13 further includes a resistor 133 and switch switches 134-137 (hereinafter referred to as the second switch 134, the third switch 135, the fourth switch 136, and the fifth switch 137, respectively) . One end of the resistor 133 is coupled to the AC coupling capacitor 131 and the first switch 132, and the other end of the resistor 133 is coupled to the switch switches 134 and 135. The second switch 134 is coupled between the resistor 133 and the ground, and the third switch 135 is coupled between the resistor 133 and the bias power supply. On the other hand, the amplifier circuit 14 includes an operational amplifier 141 and resistors 142 and 143. The resistors 142 and 143 determine the magnification between the input signal and the output signal of the operational amplifier 141. The operational amplifier 141 includes an output terminal, a positive input terminal, and a negative input terminal. Among them, the positive input terminal of the operational amplifier 141 is coupled to the AC coupling capacitor 131, the first switch 132 and the resistor 133, the operational amplifier 141 has a negative feedback amplifying circuit, and the output terminal of the operational amplifier 141 is coupled to its negative via a resistor 142. The input terminal, that is, the resistor 142 is coupled between the output terminal of the operational amplifier 141 and the input terminal of the operational amplifier 141. In addition, the resistor 143, which together with the resistor 142 determines the aforementioned magnification, is coupled between the negative input terminal of the operational amplifier 141 and the fourth switch 136, and the fifth switch 137 is coupled between the resistor 143 and the ground terminal. , And the resistor 143 is coupled between the negative input terminal of the operational amplifier 141 and the fifth switch 137, and the fourth switch 136 is coupled between the resistor 143 and the bias power supply.

Based on this, when the light sensing device 1 is in the AC coupling mode, the control circuit 16 controls the second switch 134 to turn on and controls the third switch 135 to turn off, and the resistor 133 is coupled to the ground terminal via the second switch 134 without passing through the second switch 134. The three switch 135 is coupled to the bias power supply, and the control circuit 16 controls the fifth switch 137 to turn on and controls the fourth switch 136 to turn off. The resistor 143 is coupled to the ground terminal via the fifth switch 137 and not via the fourth switch 136. Coupled to the bias power supply. Therefore, the positive input terminal of the operational amplifier 141 is coupled to the ground terminal through the resistor 133 and the second switch 134, and the negative input terminal of the operational amplifier 141 is coupled to the ground terminal through the resistor 143 and the fifth switch 137. Based on the aforementioned configuration, The operational amplifier 141 amplifies the voltage signal containing the AC component after filtering the DC component by the AC coupling capacitor 131 according to the amplification factor determined by the resistors 142 and 143 to generate the first output signal.

On the other hand, when the light sensing device 1 is in the DC coupling mode, the control circuit 16 controls the second switch 134 to turn off and controls the third switch 135 to turn on, and the resistor 133 is coupled to the bias power supply via the third switch 135. The second switch 134 is coupled to the ground, and the control circuit 16 controls the fifth switch 137 to turn off and controls the fourth switch 136 to turn on. The resistor 143 is coupled to the bias power supply via the fourth switch 136 and not via the fifth switch. 137 is coupled to the ground terminal. Therefore, the positive input terminal of the operational amplifier 141 is coupled to the bias power supply via the resistor 133 and the third switch 135, the negative input terminal of the operational amplifier 141 is coupled to the bias power supply via the resistor 143 and the fourth switch 136, and the operational amplifier 141 is based on The magnification rate determined by the resistors 142 and 143 amplifies the voltage signal including the DC component and the AC component transmitted by the first switch 132 to generate a second output signal, which is based on the fact that the positive input terminal and the negative input terminal of the operational amplifier 141 are both coupled In the configuration of the bias power supply, the operational amplifier 141 amplifies the current signal generated by the sensing circuit 11 without amplifying the DC signal contained in the bias power supply.

In one embodiment, the amplifying circuit 14 further includes a capacitor 144 coupled between the negative input terminal of the operational amplifier 141 and the output terminal of the operational amplifier 141, and the capacitor 144 is connected in parallel with the resistor 142. The capacitor 144 can filter out high frequency impurities. News. Furthermore, the resistors 142 and 143 are variable resistors with adjustable resistance values, and the resistance values of the resistors 142 and 143 are controlled by the control circuit 16, so that the operational amplifier 141 has an adjustable magnification and can generate a corresponding magnification. The first output signal and the second output signal.

In one embodiment, the light sensing device 1 further includes a bias circuit 15 coupled to the sensing circuit 11. The bias circuit 15 includes bias resistors 151, 152, and 153. The bias resistors 151, 152 are coupled between the power terminal and the ground terminal. The bias resistor 153 is coupled to the connection point between the bias resistors 151, 152. Through the bias resistors 151, 152, and 153, the bias circuit 15 generates a bias signal to the sensing circuit 11 for the sensing circuit 11 to operate and detect light. Furthermore, the bias circuit 15 includes switches 154 and 155. The switch 154 is coupled between the power supply terminal and the bias resistor 151, and the switch 155 is coupled between the bias resistor 153 and the conversion circuit 12 (the switch 155 is coupled between the bias resistor 153 and the positive input terminal of the operational amplifier 121). between). The switches 154 and 155 can be controlled by the control circuit 16 to provide power-saving control. When the light sensing device 1 is not needed to detect light, the control circuit 16 can control the switches 154 and 155 to turn off to turn off the bias circuit 15 . Further, the bias circuit 15 further includes a capacitor 156 , which is coupled to both ends of the bias resistor 152. The capacitor 156 can be charged to provide a voltage stabilizing function, and after the capacitor 156 is charged, the switch 155 can ensure the operational amplifier 121 and the sensing circuit 11 receive a stable bias signal.

In one embodiment, the light sensing device 1 may further include an input/output port P3. The input/output port P3 is located between the bias resistors 151 and 152 of the bias circuit 15. The designer of the light sensing device 1 can Add external components as required to connect the bias circuit 15 to the input port P3. Furthermore, as shown in FIG. 3, the optical sensing device 1 may further include an analog-to-digital conversion circuit (ADC) 17. The analog-to-digital conversion circuit 17 may be coupled to the output terminal of the operational amplifier 121, and the analog-to-digital conversion circuit 17 may The voltage signal generated by the amplifier 121 is converted into a digital signal, which can be used by other circuits inside the light sensing device 1 or other circuits outside the light sensing device 1; alternatively, the analog-to-digital conversion circuit 17 can also be coupled to the operational amplifier 141 At the output end, the analog-to-digital conversion circuit 17 can convert the first output signal and the second output signal generated by the operational amplifier 141 into digital signals for other circuits in the light sensing device 1 or external to the light sensing device 1 Other circuits are applied.

In one embodiment, the light sensing device 1 can be used in a fire fighting system. The light sensing device 1 is a smoke sensor, that is, the sensing circuit 11 can further include other light-emitting units to generate an infrared light. When smoke enters the light sensing device 1, the smoke particles cause the infrared light beam to scatter, so that the photoelectric crystal or light diode of the sensing circuit 11 receives the scattered light. When the amount of smoke increases, the photoelectric crystal or photodiode receives more light, and the stronger the light, the greater the reverse current generated by the photoelectric crystal or photodiode. Figures 4 and 5 illustrate that when the light intensity increases, the optoelectronic crystal or photodiode generates a larger reverse current. Therefore, when the amount of smoke in the environment is greater, the reverse current generated by the photoelectric crystal or photodiode is greater, and the sensing circuit 11 can generate a corresponding current signal. According to the photoelectric crystal or photodiode produced by different manufacturers, the sensor The current value of the current signal generated by the measuring circuit 11 is in the range of 100 pA to 1 uA.

To sum up, according to one embodiment of the light sensing device of this case, the light sensing device is equipped with multiple switchable circuits, the light sensing device can be set to DC coupling mode or AC coupling mode, and the operational amplifier The magnifications are adjustable, and the light sensing device has further built-in input and output ports reserved for external connection. The light sensing device can be adjusted and added to the circuit according to the characteristics of the photodiode of different photoelectric crystals on the market. The components greatly enhance the flexibility of its design and maintenance, and can meet most photoelectric smoke detection applications on the market. In addition, in this case, passive components, filter circuits and operational amplifiers are integrated, thereby reducing the number of passive components and reducing the wiring and area of the circuit board layout.

Although this case has been disclosed by the examples above, it is not intended to limit the case. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the case. Therefore, the scope of protection of this case The scope of the patent application attached hereafter shall prevail.

1: Light sensing device 11: Sensing circuit 12: Conversion circuit 121: Operational amplifier 122: resistance 123: Capacitance 13: Coupling mode selection circuit 131: AC coupling capacitor 132: The first switch 133: Resistance 134: The second switch 135: The third switch 136: The fourth switch 137: Fifth toggle switch 14: Amplifying circuit 141: Operational amplifier 142: Resistance 143: Resistance 144: Capacitor 15: Bias circuit 151-153: Bias resistor 154-155: Switch 156: Capacitor 16: control circuit 17: Analog-to-digital conversion circuit P1: Input and output port P2: I/O port P3: I/O port

[Fig. 1] is a block diagram of an embodiment of the light sensing device according to the present invention. [Fig. 2] is a circuit diagram of an embodiment of the light sensing device in Fig. 1. [Fig. [Fig. 3] is a circuit diagram of another embodiment of the light sensing device in Fig. 1. [Fig. [Fig. 4] is a circuit diagram of an embodiment of the photoelectric crystal or photodiode included in the sensing circuit of Fig. 1. [Fig. [Figure 5] is a schematic diagram of the current versus bias curve of the photoelectric crystal or photodiode in Figure 4.

1: Light sensing device

11: Sensing circuit

12: Conversion circuit

13: Coupling mode selection circuit

14: Amplifying circuit

15: Bias circuit

16: control circuit

Claims (15)

A light sensing device includes: a sensing circuit for detecting a light, and generating a corresponding current signal according to the intensity of the light; a conversion circuit for converting the current signal into a voltage signal, the voltage The signal includes an AC component and a DC component; a coupling mode selection circuit is used to filter out the DC component in the voltage signal to output the AC component, or output the AC component without filtering the DC component and the output includes the AC component and the DC Component of the voltage signal, the coupling mode selection circuit includes an AC coupling capacitor and a first switch. The AC coupling capacitor is connected in series to the conversion circuit and coupled between the conversion circuit and the amplifying circuit to filter out the The DC component in the voltage signal outputs the AC component, the first switch is connected in parallel with the AC coupling capacitor; and an amplifier circuit for amplifying the filtered DC component when the coupling mode selection circuit filters the DC component The voltage signal is used to generate an output signal, and when the coupling mode selection circuit does not filter the DC component, the voltage signal including the AC component and the DC component is amplified to generate another output signal. The light sensing device according to claim 1, further comprising a bias circuit coupled to the sensing circuit and the conversion circuit, the bias circuit generates a bias signal, and the sensing circuit is based on the bias voltage The signal operates to detect the light. The bias circuit includes: two bias resistors coupled between the power terminal and the ground terminal; and a switch coupled between one of the bias resistors and the power terminal. The light sensing device according to claim 2, further comprising an input/output port located at the connection point between the two bias resistors. The light sensing device according to claim 1, further comprising a bias circuit coupled to the sensing circuit and the conversion circuit, the bias circuit generates a bias signal, and the sensing circuit is based on the bias voltage The signal is operated to detect the light. The bias circuit includes: a first bias resistor, coupled to the power terminal; a second bias resistor, coupled to the first bias resistor and the ground terminal, and is connected to the first A bias resistor is commonly coupled between the power terminal and the ground terminal; a capacitor is connected in parallel to the second bias resistor; a third bias resistor is coupled to the first bias resistor and the second bias resistor The connection point between is coupled to one end of the capacitor; and a switch is coupled between the third bias resistor and the conversion circuit. The light sensing device according to claim 1, wherein the amplifying circuit includes an operational amplifier, the operational amplifier has a negative feedback circuit, and the coupling mode selection circuit further includes: a second switch, coupled to the AC The coupling capacitor and the first switch are coupled between the positive input terminal and the ground terminal of the operational amplifier; a third switch is coupled to the AC coupling capacitor and the first switch and is coupled to the Between the positive input terminal of the operational amplifier and the bias power supply; a fourth switch, coupled between the negative input terminal of the operational amplifier and the bias power supply; and a fifth switch, coupled between the operational amplifier Between the negative input terminal and the ground terminal. The light sensing device according to claim 1, further comprising two input and output ports respectively located at both ends of the AC coupling capacitor. The light sensing device according to claim 6, wherein the two input and output ports are used to connect to an external capacitor. The light sensing device according to claim 1, further comprising a control circuit for controlling the coupling mode selection circuit to filter out the DC component in the voltage signal and output the AC component, or to control the coupling mode selection circuit not to The DC component in the voltage signal is filtered out to output the voltage signal including the AC component and the DC component. The light sensing device according to claim 1, wherein the amplifying circuit includes an operational amplifier and a plurality of variable resistors, the operational amplifier has a negative feedback circuit, and the variable resistors are located on the negative feedback circuit. The light sensing device according to claim 1, wherein the conversion circuit includes an operational amplifier and a variable resistor, the operational amplifier has a negative feedback circuit, and the variable resistor is located on the negative feedback circuit. A light sensing device includes: a sensing circuit for detecting a light, and generating a corresponding current signal according to the intensity of the light; a conversion circuit for converting the current signal into a voltage signal, the voltage The signal includes an AC component and a DC component; a coupling mode selection circuit is used to filter out the DC component in the voltage signal to output the AC component, or output the AC component without filtering the DC component and the output includes the AC component and the DC The voltage signal of the component; An amplifier circuit for amplifying the filtered voltage signal to generate an output signal when the coupling mode selection circuit filters the DC component, and amplifies the AC component when the coupling mode selection circuit does not filter the DC component Component and the voltage signal of the DC component to generate another output signal; and a bias circuit coupled to the sensing circuit and the conversion circuit to generate a bias signal so that the sensing circuit is based on the bias The voltage signal is operated to detect the light. The bias circuit includes: two bias resistors coupled between the power terminal and the ground terminal; and a switch coupled between one of the bias resistors and the power terminal . The light sensing device according to claim 11 further includes an input/output port located at the connection point between the two bias resistors. A light sensing device includes: a sensing circuit for detecting a light, and generating a corresponding current signal according to the intensity of the light; a conversion circuit for converting the current signal into a voltage signal, the voltage The signal includes an AC component and a DC component; a coupling mode selection circuit is used to filter out the DC component in the voltage signal to output the AC component, or output the AC component without filtering the DC component and the output includes the AC component and the DC Component of the voltage signal; an amplifier circuit for amplifying the filtered voltage signal to generate an output signal when the coupling mode selection circuit filters the DC component, and the coupling mode selection circuit does not filter the DC Amplify the voltage signal including the AC component and the DC component to generate another output signal; and A bias circuit is coupled to the sensing circuit and the conversion circuit. The bias circuit generates a bias signal so that the sensing circuit operates according to the bias signal to detect the light. The bias voltage The circuit includes: a first bias resistor, coupled to the power terminal; a second bias resistor, coupled to the first bias resistor and the ground terminal, and coupled to the power terminal and the ground terminal together with the first bias resistor Between; a capacitor, connected in parallel to the second bias resistor; a third bias resistor, coupled to the connection point between the first bias resistor and the second bias resistor and coupled to the capacitor One end; and a switch, coupled between the third bias resistor and the conversion circuit. A light sensing device includes: a sensing circuit for detecting a light, and generating a corresponding current signal according to the intensity of the light; a conversion circuit for converting the current signal into a voltage signal, the voltage The signal includes an AC component and a DC component; a coupling mode selection circuit is used to filter out the DC component in the voltage signal to output the AC component, or output the AC component without filtering the DC component and the output includes the AC component and the DC Component of the voltage signal; and an amplifier circuit for amplifying the filtered voltage signal to generate an output signal when the coupling mode selection circuit filters out the DC component, and the coupling mode selection circuit does not filter the In the case of a DC component, the voltage signal including the AC component and the DC component is amplified to generate another output signal, and the amplifying circuit includes: An operational amplifier has a negative feedback circuit; and a complex variable resistor is located on the negative feedback circuit. A light sensing device includes: a sensing circuit for detecting a light, and generating a corresponding current signal according to the intensity of the light; a conversion circuit for converting the current signal into a voltage signal, the voltage The signal includes an AC component and a DC component; a coupling mode selection circuit is used to filter out the DC component in the voltage signal to output the AC component, or output the AC component without filtering the DC component and the output includes the AC component and the DC Component of the voltage signal; and an amplifier circuit for amplifying the filtered voltage signal to generate an output signal when the coupling mode selection circuit filters out the DC component, and the coupling mode selection circuit does not filter the In the case of a DC component, the voltage signal including the AC component and the DC component is amplified to generate another output signal. The amplifying circuit includes: an operational amplifier having a negative feedback circuit; and a variable resistor located in the negative feedback On the line.

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