WO2015131545A1 - 一种紫外光传感电路及感应系统 - Google Patents

一种紫外光传感电路及感应系统 Download PDF

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Publication number
WO2015131545A1
WO2015131545A1 PCT/CN2014/091061 CN2014091061W WO2015131545A1 WO 2015131545 A1 WO2015131545 A1 WO 2015131545A1 CN 2014091061 W CN2014091061 W CN 2014091061W WO 2015131545 A1 WO2015131545 A1 WO 2015131545A1
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Prior art keywords
transistor
electrode
coupled
ultraviolet light
signal
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PCT/CN2014/091061
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English (en)
French (fr)
Inventor
张盛东
廖聪维
胡治晋
李文杰
李君梅
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Peking University Shenzhen Graduate School
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Peking University Shenzhen Graduate School
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Priority to US15/123,239 priority Critical patent/US9983054B2/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44—Electric circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/429—Photometry, e.g. photographic exposure meter using electric radiation detectors applied to measurement of ultraviolet light

Definitions

  • the invention relates to the field of ultraviolet light detection, and in particular to an ultraviolet light sensing circuit and an induction system.
  • ultraviolet light detection and sensing technology is widely used in flame and heat sensing, missile tail flame detection, forest fire warning, gas explosion warning and other fields. Take the gas explosion warning as an example.
  • high-energy ray releases of different spectra, including ultraviolet rays which contain a wealth of information.
  • By detecting high-energy rays such as ultraviolet rays it is possible to report the occurrence of disasters in advance, thereby reducing the loss of life and property. Due to the high energy of ultraviolet light, it is necessary to use a semiconductor device with a large band gap for detection.
  • Wide-bandgap semiconductor materials commonly used for ultraviolet light detection include gallium arsenide (GaAs) and gallium nitride (GaN), but these wide-bandgap semiconductor materials are processed into semiconductor devices with complicated processes, high processing temperatures, and are not suitable for large areas. machining.
  • GaAs gallium arsenide
  • GaN gallium nitride
  • oxide TFTs In recent years, ultraviolet TFT detectors integrated with oxide TFTs have begun to appear internationally. Thanks to the rapid development of flat panel display technology, indium gallium zinc (IGZO) TFT has recently become a research hotspot, which may replace silicon-based TFTs and become the next generation of mainstream TFTs. It is worth noting that the electrical properties of oxide TFTs may change significantly under the action of ultraviolet light, such as IGZO oxides, for example, the threshold voltage is reduced, and the off-state current is increased by orders of magnitude. Therefore, it is possible to design an ultraviolet light detector using the optical-electrical characteristics of the oxide TFT. In addition, the oxide TFT has the following advantages, such as a relatively simple processing process and a low processing temperature, which is suitable for large-area production.
  • the UV detection function of the oxide TFT may even be integrated into the display panel to form a system-integrated display panel (SoP), so that the display panel can display the ultraviolet light intensity of the external environment, and even display the outside world.
  • SoP system-integrated display panel
  • the outline of the ultraviolet illuminating object is used to warn of illuminating or exploding under strong sunlight or strong infrared background interference.
  • an embodiment provides an ultraviolet light sensing circuit including a modulation unit and a phase delay unit;
  • the modulating unit includes a first stage inverter for sensing ultraviolet light and acting as a voltage feedback modulation stage;
  • the phase delay unit includes N stages of inverters connected in series, and N is an even number greater than or equal to 2;
  • the modulation unit and the phase delay unit are sequentially connected, and the output voltage of the phase delay unit is fed to the modulation unit; the modulation unit is modulated by the control signal, and the control signal is a pulse signal.
  • the ultraviolet light sensing circuit further includes an output buffer unit, and the output buffer unit includes an N+2th stage inverter, and the output buffer unit increases the driving capability of the ultraviolet light sensing circuit to the output end load.
  • the first stage inverter includes a pull-up module and a pull-down module
  • the pull-up module includes a first transistor and a second transistor, a control electrode of the first transistor and the first electrode are coupled to the control signal; a control electrode of the second transistor is coupled to the second electrode of the first transistor, and the first electrode of the second transistor Coupled to a control signal;
  • the pull-down module includes a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor, a control electrode of the third transistor is coupled to the second electrode, a first electrode is coupled to the second electrode of the first transistor, and a control electrode of the fourth transistor Coupled to the second electrode, the first electrode is coupled to the second electrode of the second transistor; the control electrode of the fifth transistor is coupled to the output of the N-stage inverter, and the first electrode is coupled to the second electrode of the third transistor, The second electrode is coupled to the low level voltage source; the control electrode of the sixth transistor is coupled to the output of the N stage inverter, the first electrode is coupled to the second electrode of the fourth transistor, and the second electrode is coupled to the low level voltage source ;
  • the third transistor and the fourth transistor are ultraviolet light sensitive transistors.
  • each of the N stages of inverters has the same circuit structure, including a seventh transistor, an eighth transistor, a ninth transistor, and a tenth transistor;
  • a control electrode of the seventh transistor and the first electrode are coupled to the control signal; a control electrode of the eighth transistor is coupled to the second electrode of the seventh transistor, a first electrode of the eighth transistor is coupled to the control signal; and a control electrode of the ninth transistor is coupled To a second electrode of the second transistor, the first electrode is coupled to the second electrode of the seventh transistor, the second electrode is coupled to the low level voltage source; the control electrode of the tenth transistor is coupled to the control electrode of the ninth transistor, first An electrode is coupled to the second electrode of the eighth transistor, the second electrode being coupled to the low level voltage source.
  • the ninth transistor and the tenth transistor are ultraviolet light sensitive transistors.
  • the first stage inverter includes a pull-up module and a pull-down module
  • the pull-up module includes a first transistor and a second transistor, a control electrode of the first transistor and the first electrode are coupled to the control signal; a control electrode of the second transistor is coupled to the second electrode of the first transistor, and the first electrode of the second transistor Coupled to a control signal;
  • the pull-down module includes a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor, a control electrode of the third transistor is coupled to the first control signal, a first electrode is coupled to the second electrode of the first transistor, and a fourth transistor is controlled
  • the pole is coupled to the first control signal, the first electrode is coupled to the second electrode of the second transistor;
  • the control pole of the fifth transistor is coupled to the input of the N-stage inverter
  • the first electrode is coupled to the second electrode of the third transistor, the second electrode is coupled to the low-level voltage source;
  • the control electrode of the sixth transistor is coupled to the output of the N-stage inverter, and the first electrode is coupled to the first a second electrode of the four transistor, the second electrode being coupled to the low level voltage source;
  • the third transistor and the fourth transistor are ultraviolet light sensitive transistors.
  • the first stage inverter includes a pull-up module and a pull-down module
  • the pull-up module includes a first transistor and a second transistor, a control electrode of the first transistor and the first electrode being coupled to the high level signal; a control electrode of the second transistor coupled to the second electrode of the first transistor, the first of the second transistor The electrode is coupled to a high level signal;
  • the pull-down module includes a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, and a fifteenth transistor, a control electrode of the third transistor is coupled to the control signal, a first electrode is coupled to the second electrode of the first transistor, and a fourth The control electrode of the transistor is coupled to the control signal, the first electrode is coupled to the second electrode of the second transistor; the control electrode of the fifth transistor is coupled to the output of the N-stage inverter, and the first electrode is coupled to the second of the third transistor An electrode; a control electrode of the sixth transistor coupled to the output of the N-stage inverter, a first electrode coupled to the second electrode of the fourth transistor; a first electrode of the fifteenth transistor coupled to the second electrode of the fifth transistor, respectively And a second electrode of the sixth transistor, the control electrode and the second electrode of the fifteenth transistor are coupled to a low level voltage source, and the fifteenth transistor is an ultraviolet light sensitive transistor.
  • the N+2th stage inverter includes an eleventh transistor, a twelfth transistor, a thirteenth transistor, and a fourteenth transistor;
  • the control electrode of the eleventh transistor and the first electrode are coupled to the control signal; the control electrode of the twelfth transistor is coupled to the second electrode of the eleventh transistor, and the first electrode of the twelfth transistor is coupled to the control signal, twelfth a second electrode of the transistor is coupled to the output; a control electrode of the thirteenth transistor is coupled to an output of the N-stage inverter, and a first electrode of the thirteenth transistor is coupled to a second electrode of the eleventh transistor, thirteenth a second electrode of the transistor is coupled to the low level voltage source; a control electrode of the fourteenth transistor is coupled to the output of the N stage inverter, and a first electrode of the fourteenth transistor is coupled to the second electrode of the twelfth transistor, The second electrode of the thirteenth transistor is coupled to a low level voltage source.
  • the ultraviolet light sensitive transistor is a zinc-based oxide thin film transistor.
  • an embodiment provides an ultraviolet light sensing system including an ultraviolet light signal transmitter, an ultraviolet light signal receiver, and an ultraviolet light sensing circuit provided by the first aspect of the present application;
  • the output end of the ultraviolet light sensing circuit is coupled to the ultraviolet light signal transmitter, the ultraviolet light signal transmitter is configured to emit a signal transmitted by the ultraviolet light sensing circuit, and the ultraviolet light signal receiver is configured to receive the signal transmitted by the ultraviolet light signal transmitter, and according to The received signal determines whether the ultraviolet light sensing circuit is exposed to ultraviolet light.
  • the ultraviolet light signal transmitter is an ultrasonic transducer for generating an ultrasonic signal and transmitting the ultrasonic wave under the excitation of an output voltage signal of the ultraviolet light sensing circuit.
  • the ultraviolet light signal receiver receives the ultrasonic signal, reduces the ultrasonic signal into an electrical signal, and determines whether the ultraviolet light sensing circuit is exposed to ultraviolet light according to the electrical signal.
  • the modulation unit in the ultraviolet light sensing circuit comprises a first stage inverter, the first stage inverter comprises an ultraviolet light sensitive transistor capable of sensing an ultraviolet light signal; and the phase delay unit comprises a smooth
  • the N-stage inverter connected in series, the output voltage of the phase delay unit is fed back to the modulation unit, the first-stage inverter in the modulation unit is modulated by the control signal, and the ultraviolet light sensing circuit can output the amplitude-modulated wave signal, which facilitates the signal. Long distance wireless transmission.
  • Figure 1 is an I-V response curve of an oxide TFT under ultraviolet light and no ultraviolet light irradiation
  • FIG. 2 is a circuit diagram of an ultraviolet light sensing circuit in the first embodiment of the present application.
  • FIG. 3 is a circuit diagram of an ultraviolet light sensing circuit in the second embodiment of the present application.
  • FIG. 5 is a schematic diagram of waveforms of an ultraviolet light sensing circuit outputted under different illumination conditions in the second embodiment of the present application;
  • FIG. 6 is a circuit diagram of an ultraviolet light sensing circuit in Embodiment 3 of the present application.
  • FIG. 7 is a circuit diagram of an ultraviolet light sensing circuit in Embodiment 4 of the present application.
  • Embodiment 8 is a circuit diagram of an ultraviolet light sensing circuit in Embodiment 5 of the present application.
  • Embodiment 9 is an operation waveform diagram of an ultraviolet light sensing circuit in Embodiment 5 of the present application.
  • FIG. 10 is a schematic diagram of an ultraviolet light sensing system in Embodiment 6 of the present application.
  • the idea of the present application is that a large number of carriers are induced in the active region of the ultraviolet light sensitive transistor exposed to high energy ultraviolet light, so that the threshold voltage of the ultraviolet light sensitive transistor is reduced, and the off-state leakage current is increased by an order of magnitude.
  • the ultraviolet light can modulate the equivalent on-resistance of the ultraviolet light sensitive transistor, so the sensing circuit can be designed with the adjustable characteristics of the resistor.
  • the transistor may be a Field Effect Transistor (FET) or a Bipolar Junction Transistor (BJT).
  • FET Field Effect Transistor
  • BJT Bipolar Junction Transistor
  • the control electrode refers to the gate
  • the first electrode refers to the drain
  • the second electrode refers to the source
  • the control electrode refers to the base
  • the first electrode refers to the collector
  • the second electrode refers to the emitter. pole.
  • the ultraviolet light sensitive transistor in the present application is exemplified by a zinc-based (Zn) oxide thin film transistor.
  • the inverters of the stages are cascaded.
  • the number of inverters of the first and last cascades is an odd number of 3 or more, which satisfies the phase condition of the oscillation circuit.
  • FIG. 1 is an IV response curve of an oxide TFT under ultraviolet light and non-ultraviolet light irradiation. It can be seen from the figure that the threshold voltage of the oxide TFT is large when there is no ultraviolet light irradiation; when the ultraviolet light is irradiated, the threshold voltage of the oxide TFT is decreased, and the subthreshold region is directed to the negative gate voltage. mobile. Taking V GS as 0 as an example, the value of I DS is about 1 pA in the absence of ultraviolet light irradiation; when there is ultraviolet light irradiation, the value of I DS is increased to about 1 nA.
  • the subthreshold circuit Under the action of ultraviolet light, the subthreshold circuit has undergone nearly three orders of magnitude change, that is, the on-resistance of the oxide TFT is changed by ultraviolet light by three orders of magnitude.
  • This application uses the TFT on-resistance to be modulated by ultraviolet light. The features are designed for circuit design.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the ultraviolet light sensing circuit in this embodiment includes a modulation unit and a phase delay unit.
  • the modulation unit and the phase delay unit are sequentially connected.
  • the output voltage of the phase delay unit is fed to the modulation unit, and the modulation unit and the phase delay unit constitute a ring oscillator.
  • the modulating unit includes a first-stage inverter 11 for sensing ultraviolet light and acting as a voltage feedback modulation stage.
  • the phase delay unit includes N stages of inverters connected in series, and the N stage inverter includes a second stage inverter to an N+1th stage inverter, and N is an even number greater than or equal to 2.
  • N 2
  • the phase delay unit includes a second stage inverter 21 and a third stage inverter 22, and the first stage inverter 11, the second stage inverter 21, and the third stage are inverted.
  • the devices 22 are sequentially connected, and the output voltage of the third-stage inverter 22 is fed to the first-stage inverter 21.
  • the first stage inverter 11 of the modulation unit is modulated by a control signal V CTR , and the control signal V CTR is a high and low level phase pulse signal.
  • the first stage inverter 11 includes a pull-up module and a pull-down module;
  • the pull-up module includes a first transistor T1 and a second transistor T2, the control electrode and the first electrode of the first transistor T1 are coupled to the control signal V CTR ;
  • the control electrode of T2 is coupled to the second electrode of the first transistor T1, the first electrode of the second transistor T2 is coupled to the control signal V CTR ;
  • the pull-down module includes a third transistor T3, a fourth transistor T4, a fifth transistor T5, and a sixth Transistor T6, the control electrode of the third transistor T3 is coupled to the second electrode, the first electrode is coupled to the second electrode of the first transistor T1;
  • the control electrode of the fourth transistor T4 is coupled to the second electrode, and the first electrode is coupled to the second electrode
  • the second electrode of the transistor T2; the third transistor T3 and the fourth transistor T4 are ultraviolet light sensitive transistors.
  • the control transistor of the fifth transistor T5 is coupled to the output terminal V OUT of the third-stage inverter 22, the first electrode is coupled to the second electrode of the third transistor T3, and the second electrode is coupled to the low-level voltage source V L ;
  • the control transistor of the six transistor T6 is coupled to the output terminal V OUT of the third stage inverter 22, the first electrode is coupled to the second electrode of the fourth transistor T4, and the second electrode is coupled to the low level voltage source V L ;
  • Transistor T5 and sixth transistor T6 receive the feedback signal of third stage inverter 22, pulling the output port of the pull-up module down to a low level voltage.
  • the first transistor T1 and the second transistor T2 form a "Darlington Transistor".
  • the pull-up module When the pull-up module outputs a high level, the second transistor T2 can pull up the output to a full-scale high potential by bootstrap action.
  • the pull-down module is divided into two paths, the first pull-down branch is composed of a third transistor T3 and a fifth transistor T5, and the second pull-down branch is composed of a fourth transistor T4 and a sixth transistor T6, and the function of the first pull-down branch is Internal node of Darlington structure Pulling down the low-level voltage makes the inverter's output voltage lower, and the second pull-down branch is used to pull down the output node.
  • the circuit structure of the second-stage inverter 21 and the third-stage inverter 22 is the same.
  • the circuit structure of the second-stage inverter 21 is introduced as an example, including the seventh transistor T17, the eighth transistor T18, and the ninth transistor. T19 and a tenth transistor T10; wherein the pull-up portion includes a seventh transistor T17 and an eighth transistor T18, and the pull-down portion includes a ninth transistor T19 and a tenth transistor T10.
  • the control electrode of the seventh transistor T17 and the first electrode are coupled to the control signal V CTR ;
  • the control electrode of the eighth transistor T18 is coupled to the second electrode of the seventh transistor T17 , and the first electrode of the eighth transistor T18 is coupled to the control signal V CTR ;
  • ninth transistor T19 a control electrode coupled to the second electrode of the second transistor T2, a first electrode coupled to the second electrode of the seventh transistor T17, the second source electrode is coupled to the low level voltage V L;
  • the tenth transistor T10 the control electrode of the ninth transistor T19 is coupled to the control electrode, a first electrode coupled to the second electrode of the eighth transistor T18, the second electrode is coupled to the low level voltage source V L.
  • the control electrodes of the ninth transistor T29 and the tenth transistor T20 of the third-stage inverter 22 are respectively coupled to the second electrode of the eighth transistor T18 of the second-stage inverter 21; the eighth of the third-stage inverter 22 A second electrode of transistor T28 is coupled to an output terminal VOUT , and an output terminal VOUT serves as a signal output terminal of the third stage inverter 22 and the ultraviolet light sensing circuit.
  • the first stage inverter in the modulating unit comprises a third transistor and a fourth transistor sensitive to ultraviolet light
  • the circuit can sense ultraviolet light
  • the third stage of the phase delay unit The phaser output voltage is fed back to the first stage inverter such that the first stage inverter, the second stage inverter and the third stage inverter form a ring oscillator circuit.
  • the ultraviolet light sensitive transistor is irradiated with ultraviolet light
  • the ring oscillator can generate an oscillating wave
  • the first stage inverter in the ring oscillator is modulated by the control signal
  • the ultraviolet light sensing circuit can output the amplitude modulated wave signal, increasing the signal.
  • the wireless transmission distance facilitates subsequent transmission of the signal to the receiver.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • the "loading effect" of the ultraviolet light sensing circuit in the first embodiment is serious: when the load capacitance is greater than a certain critical value, the output port potential of the circuit is clamped by the load capacitance at a fixed potential, and the response speed of the circuit is pulled down. The output frequency of the ring oscillator is reduced or even stopped.
  • the present embodiment is different from the first embodiment in that an output buffer unit is added, an input end of the output buffer unit is coupled to an output end of the phase delay unit, and the output buffer unit includes an N+2 level inverse.
  • the phaser, the output buffer unit is used as an output buffer stage for driving the load. Referring to FIG. 3, in the embodiment, the output buffer unit includes a fourth-stage inverter 31.
  • the ultraviolet light sensing circuit is formed by cascading four-stage inverters, and includes a first-stage inverter 11, a second-stage inverter 21, a third-stage inverter 22, and a fourth-stage inverter 31.
  • the first stage inverter 11 is a voltage feedback modulation stage, and the output of the third stage inverter 22 is fed back to the first stage inverter 11, the first stage inverter 11, the second stage inverter 21 and the
  • the three-stage inverter 22 constitutes a ring oscillator; the fourth stage inverter 31 serves as an output buffer stage to provide sufficient drive capability to the load.
  • the fourth stage inverter 31 includes an eleventh transistor T11, a twelfth transistor T12, a thirteenth transistor T13 and a fourteenth transistor T14;
  • the control electrode of the eleventh transistor T11 and the first electrode are coupled to the control signal V CTR ;
  • the control electrode of the twelfth transistor T12 is coupled to the second electrode of the eleventh transistor T11, and the first electrode of the twelfth transistor T12 is coupled to Control signal V CTR , the second electrode of the twelfth transistor T12 is coupled to the output terminal V OUT ;
  • the control electrode of the thirteenth transistor T13 is coupled to the output terminal of the third-stage inverter 22, the first of the thirteenth transistor T13 the second electrode of the eleventh transistor T11 is coupled to the second electrode of the thirteenth transistor T13 is coupled to a low voltage source V L;
  • control electrode of the fourteenth transistor T14 is coupled to a control electrode of the thirteenth transistor T13 , a first electrode of the fourteenth transistor is coupled to the second electrode of the twelfth transistor T14, T12, and T13 of the second electrode of the thirteenth transistor is coupled to a low voltage source V L.
  • the first-stage inverter 11, the second-stage inverter 21, and the third-stage inverter 22, which are cascaded in the circuit, constitute a ring oscillator, and when the control signal V CK is high, the odd-numbered phase is inverted.
  • the feedback function of the third stage inverter 22 generates a sine wave, which is output to the output terminal V OUT through the fourth stage inverter 31.
  • the frequency of the sine wave is determined by the propagation delay time of the three-stage inverter. Assuming that the delay times of the three-stage inverter are t d1 , t d2 , t d3 , the frequency of the output signal can be approximated as
  • control signal V CTR When the control signal V CTR is low, there is no high level voltage in the circuit, so the output will be pulled down to the low level voltage V L .
  • the control signal V CTR is a high and low level phase control signal, and the output of the ultraviolet sensor circuit is a pulse waveform modulated by the control signal V CTR .
  • the pull-down module of the first stage inverter 11 is equivalent to being turned off, and the output of the third stage inverter 22 cannot function through the feedback loop, maintaining the oscillation of the ring oscillator.
  • the control signal V CTR is at a high level, the outputs of the first-stage inverter 11 and the third-stage inverter 22 will remain at a high level, the responsive second-stage inverter 21 and the fourth-stage inverter The output of 31 remains low.
  • the output of each stage of the inverter in the circuit is low. Therefore, regardless of whether the modulation control signal V CTR is at a high level or a low level, the output of the ultraviolet sensing circuit is a low level voltage in the absence of ultraviolet light.
  • the ultraviolet light sensing circuit in the present application is not limited to the cascade of the four-stage inverter. Except for the inverter of the output buffer stage, the number of inverters of the head-to-tail cascade may form a normal ring oscillator structure as long as it is an odd number of 3 or more. It can be seen from equation (1) that in the case where the number of inverter stages is larger, the delay time is larger and the frequency of the output oscillation is lower. Therefore, the actual number of stages is determined according to the requirements of the process and application of the TFT.
  • FIG. 4 is a waveform diagram showing the operation of an ultraviolet light sensing circuit having a carrier modulation function in the present embodiment when ultraviolet light is present. From the point of view of the waveform output during the high-level control signal V CTR, the circuit satisfies the starting conditions; whereas during the low-level control signal V CTR, the output voltage is low.
  • the frequency of the modulation control signal V CTR is 50 kHz, and the oscillation frequency of the output signal is about 600 kHz.
  • the ultraviolet light sensing circuit in this embodiment can correctly generate an output signal having a carrier modulation function in the presence of ultraviolet light.
  • Figure 5 is a comparison diagram of the output waveforms of the circuit in the present embodiment in the presence of ultraviolet light and in the absence of ultraviolet light.
  • the circuit output is a pulse voltage with carrier modulation.
  • the output waveform is disturbed and raised at the rising edge of the control signal V CTR , but a regular oscillation waveform cannot be formed, so the output remains almost at a low level.
  • the ultraviolet light sensing circuit of this embodiment is capable of sensing ultraviolet light, and the output waveform has a significant difference in both cases.
  • the fourth-stage inverter is introduced into the ultraviolet light sensing circuit of the embodiment as an output buffer stage, which reduces the influence of the applied load on the oscillation frequency, even in the case where the external load change is large, the ultraviolet light sensing circuit
  • the output is still a sine wave with a relatively stable output frequency.
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • the present embodiment is different from the second embodiment in that the control electrodes of the third transistor T3 and the fourth transistor T4 in the first-stage inverter 41 are connected to the first control signal V C .
  • the photo-generated carriers have a long process of disappearance after the ultraviolet light is removed, which will affect the detection of two ultraviolet light events that occur closer together. If the carrier increase caused by the last ultraviolet light is present for a long time, the ultraviolet light sensing circuit may generate an erroneous response even if there is no ultraviolet light in the next detection process.
  • the control electrodes of the third transistor T3 and the fourth transistor T4 are connected to the first control signal V C , and the third transistor T3 and the fourth transistor are used by the first control signal V C .
  • Transistor T4 performs control.
  • the first control signal V C jumps from a high level to a low level, which can accelerate the disappearance of the photo-generated carriers, reduce signal crosstalk in the adjacent detection time, and improve the detection accuracy.
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the difference between this embodiment and the second embodiment is that the ninth transistor T19 and the tenth transistor T10 in the second-stage inverter 21 and the ninth transistor T29 in the third-stage inverter 22 And the tenth transistor T20 is an ultraviolet light sensitive transistor.
  • the frequency of the ring oscillator output signal is mainly determined by the delay time of each stage inverter: the delay time of each stage inverter is reduced, and the frequency of the output signal will be increased.
  • the ninth transistor T19 and the tenth transistor T10 of the second-stage inverter 21 and the ninth transistor T29 and the tenth transistor T20 of the third-stage inverter 22 are both ultraviolet light-sensitive transistors and both Under the ultraviolet light, the delay time of the three-stage inverter is reduced, thereby increasing the frequency of the output signal.
  • Embodiment 5 is a diagrammatic representation of Embodiment 5:
  • the ultraviolet light sensing circuit in this embodiment is different from the second embodiment in the first stage inverter 51.
  • the circuit is not changed, and details are not described herein again.
  • the first stage inverter 51 in this embodiment includes a pull-up module and a pull-down module;
  • the pull-up module includes a first transistor T1 and a second transistor T2, and the control electrode and the first electrode of the first transistor T1 are coupled to a high level signal.
  • V DD the control electrode of the second transistor T2 is coupled to the second electrode of the first transistor, and the first electrode of the second transistor is coupled to the high level signal V DD ;
  • the pull-down module includes a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, and a fifteenth transistor T15.
  • the control electrode of the third transistor T3 is coupled to the control signal V CTR , and the first electrode is coupled to the first a second electrode of the transistor T1; a control electrode of the fourth transistor T4 is coupled to the control signal V CTR , a first electrode is coupled to the second electrode of the second transistor T2 ; a control electrode of the fifth transistor T5 is coupled to the third-stage inverter At the output of 22, the first electrode is coupled to the second electrode of the third transistor T3; the control electrode of the sixth transistor T6 is coupled to the output of the third-stage inverter 22, and the first electrode is coupled to the fourth transistor T4 a second electrode; a first electrode of the fifteenth transistor T15 is coupled to a second electrode of the fifth transistor T5 and a second electrode of the sixth transistor T6, respectively, and the control electrode and the second electrode of the fifteenth transistor T15 are coupled
  • the internal node of the ring oscillator when the control signal V CTR changes from a high level to a low level, the internal node of the ring oscillator is pulled down to a low level through a pull-down circuit similar to the ninth transistor T19. Since the control signal V CTR is at a low level, the pull-down circuit is almost turned off in the second half of the pull-down, so that the pull-down of the internal node and the output node of the ultraviolet sensing circuit can only be realized by the leakage current. Although the internal node and the output node of the final UV sensing circuit will reach a stable low level potential, but limited by the value of the leakage current, the process may take a long time, and during this time, the output state of the circuit uncertain.
  • the output port When the load is a small resistive load, the output port may be pulled to a low level voltage; but when the load is a large resistive load or a capacitive load, the output port is in a floating state. Therefore, the output of the ultraviolet light sensing circuit in the first embodiment is properly matched to perform normal operation, which will limit the application of the ultraviolet light sensing circuit.
  • the output signal V OUT is modulated by the control signal V CTR : when the control signal V CTR is at a high level, the ring oscillator can normally operate in response to ultraviolet light irradiation; when the control signal V When CTR is low, the ring oscillator stops oscillating and outputs a stable low level voltage.
  • the first electrode of the transistor in the pull-up module is coupled to a high-level voltage
  • the transistor in the pull-down module is coupled to a low-level voltage
  • FIG. 9 is an operation waveform diagram of the circuit in the present embodiment when ultraviolet light is present.
  • the output can normally start up; and during the low period of the control signal V CTR , the output is a low level voltage.
  • the frequency of the control signal V CTR is 50 kHz, and the oscillation frequency of the output signal is about 500 kHz.
  • the ultraviolet light sensing circuit in this embodiment can correctly generate an output signal having a carrier modulation function in the presence of ultraviolet light.
  • the ultraviolet light sensing system in this embodiment includes an ultraviolet light signal emitter, an ultraviolet light signal receiver, and an ultraviolet light sensing circuit, and the ultraviolet light sensing circuit can be any one of the first embodiment to the fifth embodiment. Circuit.
  • the output end of the ultraviolet light sensing circuit is coupled to the ultraviolet light signal transmitter, the ultraviolet light signal transmitter is configured to emit a signal transmitted by the ultraviolet light sensing circuit, and the ultraviolet light signal receiver is configured to receive the signal transmitted by the ultraviolet light signal transmitter, and according to The received signal determines whether the ultraviolet light sensing circuit is exposed to ultraviolet light.
  • the ultraviolet light signal transmitter is an ultrasonic transducer for generating an ultrasonic signal under the excitation of an output voltage signal of the ultraviolet light sensing circuit and transmitting the ultrasonic signal; the ultraviolet light signal receiver receives the ultrasonic wave The signal is used to restore the ultrasonic signal to an electrical signal, and based on the electrical signal, determine whether the ultraviolet light sensing circuit is exposed to ultraviolet light.
  • the carrier frequency of the output signal V OUT of the ultraviolet light sensing circuit is 20 kHz, and a voltage signal of about 600 kHz is superimposed on this carrier wave, and the signal frequency is just in the ultrasonic frequency range.
  • the output signal V OUT is transmitted to the ultrasonic transducer, which energizes the ultrasonic transducer to generate an ultrasonic signal. Since the ultrasonic signal has good directivity, the ultraviolet light signal receiver will receive the modulated ultrasonic signal. The ultraviolet light signal receiver then reduces the ultrasonic signal to an electrical signal through the ultrasonic transducer. The ultraviolet light signal receiver decodes the obtained electrical signal to determine whether the received signal contains ultraviolet light irradiation information, and if the ultraviolet light irradiation information is included, an alarm operation is performed. In addition, information such as the intensity of ultraviolet light irradiation can be obtained by converting the frequency and intensity of the signal.
  • a plurality of ultraviolet light sensing nodes may be disposed within a range, and the ultraviolet light sensing nodes include an ultraviolet light sensing circuit and an ultraviolet light signal transmitter, which share an ultraviolet light signal receiver.
  • the geographic location of the ultraviolet light can be calculated from the position of the ultraviolet light sensing node.
  • the ultraviolet light sensing system can be arranged in the mountain forest as a mountain fire warning system; it can also be placed in the mine as an early warning of gas explosion; placed at a gas station, etc. Inflammable and explosive places, as a warning for fire or explosion.
  • the ultraviolet light sensitive device and the signal modulation circuit are all formed by using an oxide TFT, and the oxide TFT has low preparation cost and is convenient for large-area production, the entire ultraviolet light sensing system is inexpensive;
  • the ultraviolet light sensing system can output amplitude modulated waves, suitable for wireless communication over long distances;
  • the sensitivity to ultraviolet light is high, and the ultraviolet light of the outside can be accurately judged by the information such as the intensity and frequency of the output pulse;
  • the system configuration is flexible and applicable, and the ultraviolet sensor node and the ultraviolet light signal receiver can be distributed in a wide physical position.

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Abstract

一种紫外光传感电路及感应系统。紫外光传感电路包括调制单元和相位延迟单元；调制单元包括第一级反相器，用于感应紫外光并作为电压反馈调制级；相位延迟单元包括顺次连接的N级反相器，N为大于等于2的偶数；调制单元和相位延迟单元顺序连接，相位延迟单元的输出电压馈送至调制单元；调制单元受控制信号调制，控制信号为脉冲信号。该紫外光传感电路及感应系统可用于紫外光信息通信，该紫外光传感电路能够感应紫外光信号，输出幅度调制波信号。

Description

一种紫外光传感电路及感应系统 技术领域
本发明涉及紫外光探测领域，具体涉及一种紫外光传感电路及感应系统。
背景技术
利用高能量的紫外光设计的探测器或传感器，与传统的红外或可见光探测器和传感器相比，具有抗干扰性强，误触发、误报警概率低等优势。因此紫外光探测和传感技术被广泛应用到火焰和热传感、导弹尾焰探测、山林火灾预警、瓦斯爆炸预警等领域。以瓦斯爆炸预警为例，在瓦斯爆炸之前有不同频谱的高能量射线释放，其中包括紫外线，这些射线中蕴含着丰富的信息。通过对紫外线等高能量射线的探测，可以提前报告灾难的发生，从而减少生命财产损失。由于紫外光能量高，必须采用禁带宽度较大的半导体器件进行探测。常用于紫外光探测的宽禁带半导体材料包括砷化镓(GaAs)和氮化镓(GaN)等，但是这些宽禁带半导体材料加工成半导体器件时工艺复杂，加工温度高，不适于大面积加工。
近年来，国际上开始出现氧化物TFT集成的紫外光探测器。得益于平板显示技术的迅速发展，铟镓锌(IGZO)TFT最近成为研究热点，其可能取代硅基TFT，成为下一代主流的TFT。值得关注的是，IGZO等氧化物在紫外光作用下，氧化物TFT的电学特性可能发生显著的改变，例如，阈值电压减小，关态电流呈数量级地增加等。因此，可能利用氧化物TFT的光-电特性设计紫外光探测器。此外，氧化物TFT还具有如下的一些优点，例如：加工工艺相对简单，加工温度低，适合于大面积生产。氧化物TFT的紫外探测功能甚至可能被集成于显示面板中，构成系统集成的显示面板(System on Panel，SoP)，于是显示面板除还有可能读出外界环境的紫外光强度，甚至显示出外界紫外发光物体的轮廓，对强日光或者强红外背景干扰情况下的发光或者爆炸进行预警。
迄今为止尚未出现成熟的基于氧化物TFT的紫外光传感电路方案，尤其是山林火灾或者瓦斯爆炸预警等应用场合，紫外光信号的检测及检测信号的传输还是亟待解决的问题。
发明内容
本发明的目的是提供一种能够感应紫外光并输出幅度调制波的紫外光传感电路及感应系统。
依据本发明第一方面，一种实施方式提供一种紫外光传感电路，包括调制单元和相位延迟单元；
调制单元包括第一级反相器，用于感应紫外光并作为电压反馈调制级；
相位延迟单元包括顺次连接的N级反相器，N为大于等于2的偶数；
调制单元和相位延迟单元顺序连接，相位延迟单元的输出电压馈送至调制单元；调制单元受控制信号调制，控制信号为脉冲信号。
作为一种优选的实施方式，紫外光传感电路还包括输出缓冲单元，输出缓冲单元包括第N+2级反相器，输出缓冲单元提高紫外光传感电路对输出端负载的驱动能力。
在一种实施方式中，第一级反相器包括上拉模块和下拉模块；
上拉模块包括第一晶体管和第二晶体管，第一晶体管的控制极和第一电极耦合至控制信号；第二晶体管的控制极耦合至第一晶体管的第二电极，第二晶体管的第一电极耦合至控制信号；
下拉模块包括第三晶体管、第四晶体管、第五晶体管和第六晶体管，第三晶体管的控制极耦合到第二电极，第一电极耦合至第一晶体管的第二电极；第四晶体管的控制极耦合到第二电极，第一电极耦合至第二晶体管的第二电极；第五晶体管的控制极耦合至N级反相器的输出端，第一电极耦合至第三晶体管的第二电极，第二电极耦合至低电平电压源；第六晶体管的控制极耦合至N级反相器的输出端，第一电极耦合至第四晶体管的第二电极，第二电极耦合至低电平电压源；
第三晶体管和第四晶体管为紫外光敏感晶体管。
作为一种实施方式，N级反相器中每一级反相器的电路结构相同，包括第七晶体管、第八晶体管、第九晶体管和第十晶体管；
第七晶体管的控制极和第一电极耦合至控制信号；第八晶体管的控制极耦合至第七晶体管的第二电极，第八晶体管的第一电极耦合至控制信号；第九晶体管的控制极耦合至第二晶体管的第二电极，第一电极耦合至第七晶体管的第二电极，第二电极耦合至低电平电压源；第十晶体管的控制极耦合至第九晶体管的控制极，第一电极耦合至第八晶体管的第二电极，第二电极耦合至低电平电压源。
作为一种实施方式，第九晶体管和第十晶体管为紫外光敏感晶体管。
在一种实施方式中，第一级反相器包括上拉模块和下拉模块；
上拉模块包括第一晶体管和第二晶体管，第一晶体管的控制极和第一电极耦合至控制信号；第二晶体管的控制极耦合至第一晶体管的第二电极，第二晶体管的第一电极耦合至控制信号；
下拉模块包括第三晶体管、第四晶体管、第五晶体管和第六晶体管，第三晶体管的控制极耦合至第一控制信号，第一电极耦合至第一晶体管的第二电极；第四晶体管的控制极耦合至第一控制信号，第一电极耦合至第二晶体管的第二电极；第五晶体管的控制极耦合至N级反相器的输 出端，第一电极耦合至第三晶体管的第二电极，第二电极耦合至低电平电压源；第六晶体管的控制极耦合至N级反相器的输出端，第一电极耦合至第四晶体管的第二电极，第二电极耦合至低电平电压源；
第三晶体管和第四晶体管为紫外光敏感晶体管。
在一种实施方式中，第一级反相器包括上拉模块和下拉模块；
上拉模块包括第一晶体管和第二晶体管，第一晶体管的控制极和第一电极耦合至高电平信号；第二晶体管的控制极耦合至第一晶体管的第二电极，第二晶体管的第一电极耦合至高电平信号；
下拉模块包括第三晶体管、第四晶体管、第五晶体管、第六晶体管和第十五晶体管，第三晶体管的控制极耦合至控制信号，第一电极耦合至第一晶体管的第二电极；第四晶体管的控制极耦合至控制信号，第一电极耦合至第二晶体管的第二电极；第五晶体管的控制极耦合至N级反相器的输出端，第一电极耦合至第三晶体管的第二电极；第六晶体管的控制极耦合至N级反相器的输出端，第一电极耦合至第四晶体管的第二电极；第十五晶体管的第一电极分别耦合至第五晶体管的第二电极和第六晶体管的第二电极，第十五晶体管的控制极和第二电极耦合至低电平电压源，第十五晶体管为紫外光敏感晶体管。
在一种实施方式中，第N+2级反相器包括第十一晶体管、第十二晶体管、第十三晶体管和第十四晶体管；
第十一晶体管的控制极和第一电极耦合至控制信号；第十二晶体管的控制极耦合至第十一晶体管的第二电极，第十二晶体管的第一电极耦合至控制信号，第十二晶体管的第二电极耦合至输出端；第十三晶体管的控制极耦合至N级反相器的输出端，第十三晶体管的第一电极耦合至第十一晶体管的第二电极，第十三晶体管的第二电极耦合至低电平电压源；第十四晶体管的控制极耦合至N级反相器的输出端，第十四晶体管的第一电极耦合至第十二晶体管的第二电极，第十三晶体管的第二电极耦合至低电平电压源。
作为一种实施方式，紫外光敏感晶体管为锌基氧化物薄膜晶体管。
依据本发明第二方面，一种实施方式提供一种紫外光感应系统，包括紫外光信号发射器、紫外光信号接收器和本申请第一方面提供的紫外光传感电路；
紫外光传感电路的输出端耦合至紫外光信号发射器，紫外光信号发射器用于发射紫外光传感电路输送的信号，紫外光信号接收器用于接收紫外光信号发射器传送的信号，并根据接收到的信号判断紫外光传感电路是否存在紫外光照射。
作为一种实施方式，紫外光信号发射器为超声波换能器，用于在紫外光传感电路的输出电压信号的激励下产生超声波信号并发射该超声波 信号；紫外光信号接收器接收超声波信号，将超声波信号还原成电信号，并根据该电信号判断紫外光传感电路是否存在紫外光照射。
依据本发明的一种实施方式中，紫外光传感电路中的调制单元包括第一级反相器，第一级反相器包括紫外光敏感晶体管，能够感应紫外光信号；相位延迟单元包括顺次连接的N级反相器，相位延迟单元的输出电压反馈至调制单元，调制单元中的第一级反相器受控制信号调制，紫外光传感电路能输出幅度调制波信号，方便了信号的长距离无线传输。
附图说明
图1是氧化物TFT在紫外光和无紫外光照射情况下的I-V响应曲线；
图2是本申请实施例一中的紫外光传感电路的电路图；
图3是本申请实施例二中的紫外光传感电路的电路图；
图4是本申请实施例二中的紫外光传感电路的工作波形图；
图5是本申请实施例二中的紫外光传感电路在不同光照条件下输出的波形示意图；
图6是本申请实施例三中的紫外光传感电路的电路图；
图7是本申请实施例四中的紫外光传感电路的电路图；
图8是本申请实施例五中的紫外光传感电路的电路图；
图9是本申请实施例五中的紫外光传感电路的工作波形图；
图10是本申请实施例六中的紫外光感应系统的示意图。
具体实施方式
本申请的思路是：暴露于高能量紫外光下的紫外光敏感晶体管有源区中会诱生出大量的载流子，于是紫外光敏感晶体管的阈值电压减小，关态漏电流呈数量级增加，换言之，紫外光可以调制紫外光敏感晶体管的等效导通电阻，于是可以利用这种电阻可调的特点设计传感电路。
首先对本申请中用到的一些术语进行说明。根据结构的不同，晶体管可能是场效应管(FET，Field Effect Transistor)或者双极型晶体管(BJT，Bipolar Junction Transistor)。当晶体管为FET时，控制极指栅极，第一电极指漏极，第二电极指源极；当晶体管为BJT时，控制极指基极，第一电极指集电极，第二电极指发射极。本申请中的紫外光敏感晶体管以锌基(Zn)氧化物薄膜晶体管为例进行说明。需要说明的是，为了描述方便，本申请实施例中取N＝2，即紫外光传感电路由4个反相器级联而成，但本申请的紫外光传感电路并不局限于4级反相器级联，实际使用时，除用作输出缓冲级的反相器外，首尾级联的反相器数量是大于等于3的奇数，就可以满足振荡电路的相位条件。
请参考图1，图1是氧化物TFT在紫外光和非紫外光照射情况下的I-V响应曲线。从图中可以看出，在没有紫外光照射时，氧化物TFT的阈值电压的值较大；在有紫外光照射时，氧化物TFT的阈值电压减小， 亚阈区域向负栅极电压方向移动。以VGS为0为例，在没有紫外光照射时，IDS的值约为1pA；当存在紫外光照射时，IDS的值增加到约1nA。在紫外光的作用下，亚阈电路发生了近三个数量级的变化，即氧化物TFT的导通电阻受紫外光的调制变化了三个数量级，本申请就是利用TFT导通电阻受紫外光调制的特点进行电路设计的。
下面通过具体实施方式结合附图对本申请作进一步详细说明。
实施例一：
本实施例中的紫外光传感电路包括调制单元和相位延迟单元，调制单元和相位延迟单元顺序连接，相位延迟单元的输出电压馈送至调制单元，调制单元和相位延迟单元构成环形振荡器。
请参考图2，在本实施例中，调制单元包括第一级反相器11，用于感应紫外光并作为电压反馈调制级。相位延迟单元包括顺次连接的N级反相器，N级反相器包括第二级反相器至第N+1级反相器，N为大于等于2的偶数。本实施例中，N＝2，相位延迟单元包括第二级反相器21和第三级反相器22，第一级反相器11、第二级反相器21和第三级反相器22顺次连接，第三级反相器22的输出电压馈送至第一级反相器21。
调制单元的第一级反相器11受控制信号VCTR调制，控制信号VCTR为高低电平相间的脉冲信号。
第一级反相器11包括上拉模块和下拉模块；上拉模块包括第一晶体管T1和第二晶体管T2，第一晶体管T1的控制极和第一电极耦合至控制信号VCTR；第二晶体管T2的控制极耦合至第一晶体管T1的第二电极，第二晶体管T2的第一电极耦合至控制信号VCTR；下拉模块包括第三晶体管T3、第四晶体管T4、第五晶体管T5和第六晶体管T6，第三晶体管T3的控制极耦合到第二电极，第一电极耦合至第一晶体管T1的第二电极；第四晶体管T4的控制极耦合到第二电极，第一电极耦合至第二晶体管T2的第二电极；第三晶体管T3和第四晶体管T4为紫外光敏感晶体管。第五晶体管T5的控制极耦合至第三级反相器22的输出端VOUT，第一电极耦合至第三晶体管T3的第二电极，第二电极耦合至低电平电压源VL；第六晶体管T6的控制极耦合至第三级反相器22的输出端VOUT，第一电极耦合至第四晶体管T4的第二电极，第二电极耦合至低电平电压源VL；第五晶体管T5和第六晶体管T6接收第三级反相器22的反馈信号，将上拉模块的输出端口下拉到低电平电压。
第一晶体管T1和第二晶体管T2构成“达林顿”结构(Darlington Transistor)，在上拉模块输出高电平时，第二晶体管T2可以通过自举作用将输出上拉到满幅值高电位。下拉模块分为两路，第一下拉支路由第三晶体管T3和第五晶体管T5组成，第二下拉支路由第四晶体管T4和第六晶体管T6组成，第一下拉支路的作用是将达林顿结构的内部节点 下拉到低电平电压，使反相器的输出电压更低，第二下拉支路的作用是下拉输出节点。
第二级反相器21和第三级反相器22的电路结构相同，这里以第二级反相器21为例介绍其电路结构，包括第七晶体管T17、第八晶体管T18、第九晶体管T19和第十晶体管T10；其中，上拉部分包括第七晶体管T17和第八晶体管T18，下拉部分包括第九晶体管T19和第十晶体管T10。第七晶体管T17的控制极和第一电极耦合至控制信号VCTR；第八晶体管T18的控制极耦合至第七晶体管T17的第二电极，第八晶体管T18的第一电极耦合至控制信号VCTR；第九晶体管T19的控制极耦合至第二晶体管T2的第二电极，第一电极耦合至第七晶体管T17的第二电极，第二电极耦合至低电平电压源VL；第十晶体管T10的控制极耦合至第九晶体管T19的控制极，第一电极耦合至第八晶体管T18的第二电极，第二电极耦合至低电平电压源VL。
第三级反相器22中第九晶体管T29和第十晶体管T20的控制极分别耦合至第二级反相器21中第八晶体管T18的第二电极；第三级反相器22中第八晶体管T28的第二电极耦合至输出端VOUT，输出端VOUT作为第三级反相器22和紫外光传感电路的信号输出端。
本实施例中的紫外光传感电路，调制单元中的第一级反相器包含对紫外光敏感的第三晶体管和第四晶体管，电路能够感应紫外光，相位延迟单元中的第三级反相器输出电压反馈至第一级反相器，使得第一级反相器、第二级反相器和第三级反相器构成环形振荡器电路。当紫外光敏感晶体管存在紫外光照射时，环形振荡器能够产生振荡波，环形振荡器中的第一级反相器受控制信号调制，紫外光传感电路能输出幅度调制波信号，增加了信号的无线传输距离，方便了信号后续传输到接收器。
实施例二：
实施例一中的紫外光传感电路“负载效应”比较严重：当负载电容大于某临界值时，电路的输出端口电位被负载电容钳位在一固定电位，于是电路的响应速度被拉低，环形振荡器的输出频率降低甚至停止振荡。为了减少这种负载效应，本实施例与实施例一的不同之处在于增加了输出缓冲单元，输出缓冲单元的输入端耦合至相位延迟单元的输出端，输出缓冲单元包括第N+2级反相器，输出缓冲单元用作驱动负载的输出缓冲级。请参考图3，在本实施例中，输出缓冲单元包括第四级反相器31。紫外光传感电路由四级反相器级联而成，包括第一级反相器11、第二级反相器21、第三级反相器22和第四级反相器31。其中第一级反相器11是电压反馈调制级，第三级反相器22的输出反馈到第一级反相器11，第一级反相器11、第二级反相器21和第三级反相器22构成环形振荡器；第四级反相器31作为输出缓冲级，给负载提供足够的驱动能力。
这里只补充说明第四级反相器31的构成及连接关系，其余与实施例一相同的部分，此处就不再赘述。第四级反相器31包括第十一晶体管T11、第十二晶体管T12、第十三晶体管T13和第十四晶体管T14；
第十一晶体管T11的控制极和第一电极耦合至控制信号VCTR；第十二晶体管T12的控制极耦合至第十一晶体管T11的第二电极，第十二晶体管T12的第一电极耦合至控制信号VCTR，第十二晶体管T12的第二电极耦合至输出端VOUT；第十三晶体管T13的控制极耦合至第三级反相器22的输出端，第十三晶体管T13的第一电极耦合至第十一晶体管T11的第二电极，第十三晶体管T13的第二电极耦合至低电平电压源VL；第十四晶体管T14的控制极耦合至第十三晶体管T13的控制极，第十四晶体管T14的第一电极耦合至第十二晶体管T12的第二电极，第十三晶体管T13的第二电极耦合至低电平电压源VL。
下面根据紫外光存在与否，对本实施例中的紫外光传感电路的工作原理分别进行介绍：
(1)存在紫外光照射时
在紫外光作用下，第三晶体管T3和第四晶体管T4内部的光生载流子数量激增，于是第三晶体管T3和第四晶体管T4的导通能力提高。电路中首尾级联的第一级反相器11、第二级反相器21和第三级反相器22构成了环形振荡器，当控制信号VCK为高电平时，由于奇数级反相器的反馈作用，第三级反相器22的输出端会产生正弦波，经第四级反相器31后输出至输出端VOUT。该正弦波的频率由这三级反相器的传输延迟时间决定，假定三级反相器的延迟时间分别为td1，td2，td3，则输出信号的频率可以近似表示为
Figure PCTCN2014091061-appb-000001
td1，td2，td3的取值与晶体管的迁移率μ、沟道长度L、驱动电压VH等参量有关，可表示如下(式中n＝1，2，3)：
Figure PCTCN2014091061-appb-000002
当控制信号VCTR为低电平时，电路中没有了高电平电压，于是输出端将被下拉到低电平电压VL。在该电路中，控制信号VCTR为高低电平相间的控制信号，紫外传感电路的输出为受到控制信号VCTR调制的脉冲波形。
(2)不存在紫外光照射时
在不存在紫外光照射时，第一级反相器11的下拉模块相当于断开，第三级反相器22的输出无法通过反馈回路起作用，维持环形振荡器的振 荡。当控制信号VCTR为高电平时，第一级反相器11和第三级反相器22的输出将保持为高电平，响应的第二级反相器21和第四级反相器31的输出保持为低电平。
当控制信号VCTR为低电平时，电路中各级反相器的输出都为低电平。因此，无论调制控制信号VCTR为高电平或者低电平，在没有紫外光照射的情况下，紫外传感电路的输出都为低电平电压。
从以上原理的分析可知，本申请中的紫外光传感电路并不局限于4级反相器的级联。除输出缓冲级的反相器之外，首尾级联的反相器数量只要是大于等于3的奇数，都可能形成正常的环形振荡器结构。由公式(1)可知，在反相器级数更多的情况下，延迟时间更大，输出振荡的频率更低。因此，实际的级数确定要根据TFT的工艺和应用的需求来确定。
图4为当存在紫外光时本实施例中的具有载波调制功能的紫外光传感电路工作波形图。从输出的波形来看，在控制信号VCTR的高电平期间，电路满足起振条件；而控制信号VCTR的低电平期间，输出为低电平电压。在这里，调制控制信号VCTR的频率是50kHz，而输出信号的振荡频率约为600kHz。从图中可以看出，本实施例中的紫外光传感电路在存在紫外光情况下能够正确地产生具有载波调制功能的输出信号。
图5为本实施例中的电路在存在紫外光时和不存在紫外光时输出波形的对比图。图5上图中，当存在紫外光时，电路输出为具有载波调制的脉冲电压。图5下图中，当不存在紫外光时，在控制信号VCTR的上升沿，输出波形会受到扰动而升高，但是无法形成规则的振荡波形，所以输出几乎保持为低电平。从图5可以看出，本实施例中的紫外光传感电路能够感应紫外光，而且输出波形在两种情况下具有显著的差异。
本实施例的紫外光传感电路中引入第四级反相器用作输出缓冲级，减少了外加负载对于振荡频率的影响，即使在外接负载变换情况较大的情况下，紫外光传感电路的输出仍然是输出频率较为稳定的正弦波。
实施例三：
请参考图6，本实施例与实施例二的不同之处在于，第一级反相器41中的第三晶体管T3和第四晶体管T4的控制极连接至第一控制信号VC。
对氧化物TFT或其他类型的紫外光探测器，一个重要的问题是紫外光撤销后，光生载流子的消逝过程较长，这将影响发生时间较接近的两次紫外光事件的探测。如果上一次紫外光引起的载流子增加长时间存在，即使下一次探测过程中没有紫外光，紫外光传感电路也可能会产生错误的响应。本实施例中，为了避免这种情况的发生，将第三晶体管T3和第四晶体管T4的控制极连接到第一控制信号VC，用第一控制信号VC对第三晶体管T3和第四晶体管T4进行控制。第一控制信号VC从高电平跳变到低电平，可以加速光生载流子的消逝，减少相邻探测时间内的信号串扰，提高探测的准确性。
实施例四：
请参考图7，本实施例与实施例二的不同之处在于，第二级反相器21中的第九晶体管T19和第十晶体管T10以及第三级反相器22中的第九晶体管T29和第十晶体管T20均为紫外光敏感晶体管。
由公式(1)可知，环形振荡器输出信号的频率主要是由各级反相器的延迟时间决定：减少各级反相器的延迟时间，输出信号的频率将会提高。本实施例中，第二级反相器21中的第九晶体管T19和第十晶体管T10以及第三级反相器22中的第九晶体管T29和第十晶体管T20均为紫外光敏感晶体管并且均置于紫外光照射下，于是这三级反相器的延迟时间均被减少，从而提高了输出信号的频率。
实施例五：
请参考图8，本实施例中的紫外光传感电路与实施例二的不同之处在于第一级反相器51，电路未发生变化的此处不再赘述。
本实施例中的第一级反相器51包括上拉模块和下拉模块；上拉模块包括第一晶体管T1和第二晶体管T2，第一晶体管T1的控制极和第一电极耦合至高电平信号VDD；第二晶体管T2的控制极耦合至第一晶体管的第二电极，第二晶体管的第一电极耦合至高电平信号VDD；
下拉模块包括第三晶体管T3、第四晶体管T4、第五晶体管T5、第六晶体管T6和第十五晶体管T15，第三晶体管T3的控制极耦合至控制信号VCTR，第一电极耦合至第一晶体管T1的第二电极；第四晶体管T4的控制极耦合至控制信号VCTR，第一电极耦合至第二晶体管T2的第二电极；第五晶体管T5的控制极耦合至第3级反相器22的输出端，第一电极耦合至第三晶体管T3的第二电极；第六晶体管T6的控制极耦合至第3级反相器22的输出端，第一电极耦合至第四晶体管T4的第二电极；第十五晶体管T15的第一电极分别耦合至第五晶体管T5的第二电极和第六晶体管T6的第二电极，第十五晶体管T15的控制极和第二电极耦合至低电平电压源VL，第十五晶体管T15为紫外光敏感晶体管。
实施例二中的电路，当控制信号VCTR由高电平变为低电平时，环形振荡器的内部节点下拉到低电平必须通过类似第九晶体管T19的下拉电路。由于控制信号VCTR为低电平，下拉电路在下拉后半段几乎处于关闭状态，于是紫外传感电路的内部节点、输出节点的下拉只能通过泄漏电流实现。虽然最终紫外传感电路的内部节点和输出节点都会达到稳定的低电平电位，但是受限于泄漏电流的值，该过程可能需要较长的时间，而在这段时间内，电路的输出状态不确定。当负载为较小的阻性负载时，输出端口可能被拉到低电平电压；但是当负载为较大的阻性负载或者容性负载时，输出端口为悬浮态。因此，实施例一中的紫外光传感电路的输出要进行适当的阻抗匹配才能够正常地工作，这将限制紫外光传感电路的应用。
本实施例中的紫外光传感电路，输出信号VOUT受控制信号VCTR的 调制：当控制信号VCTR为高电平时，环形振荡器能够响应紫外光照射而正常地工作；当控制信号VCTR为低电平时，环形振荡器停止振荡，输出稳定的低电平电压。在这种紫外传感电路里，上拉模块中晶体管的第一电极耦合到高电平电压，下拉模块中晶体管耦合到低电平电压，因此电路输出以及紫外光传感电路的内部节点总是有确定的电位状态，而不是悬浮状态，避免了实施例一中的电路存在的由于输出阻抗匹配问题而应用场合受限的问题。
请参考图9，图9为本实施例中的电路存在紫外光时的工作波形图。从图中可以看出，在控制信号VCTR的高电平期间，输出能够正常地起振；而控制信号VCTR的低电平期间，输出为低电平电压。在这里，控制信号VCTR的频率是50kHz，而输出信号的振荡频率约为500kHz，本实施例中的紫外光传感电路在存在紫外光情况下能够正确地产生具有载波调制功能的输出信号。
实施例六：
请参考图10，本实施例中的紫外光感应系统包括紫外光信号发射器、紫外光信号接收器和紫外光传感电路，紫外光传感电路可以为实施例一至实施例五中任一种电路。
紫外光传感电路的输出端耦合至紫外光信号发射器，紫外光信号发射器用于发射紫外光传感电路输送的信号，紫外光信号接收器用于接收紫外光信号发射器传送的信号，并根据接收到的信号判断紫外光传感电路是否存在紫外光照射。
作为一种实施方式，紫外光信号发射器为超声波换能器，用于在紫外光传感电路的输出电压信号的激励下产生超声波信号并将此超声波信号发射出去；紫外光信号接收器接收超声波信号，将超声波信号还原成电信号，并根据该电信号判断紫外光传感电路是否存在紫外光照射。例如，紫外光传感电路的输出信号VOUT的载波频率为20kHz，在这种载波上叠加约600kHz的电压信号，该信号频率正好在超声波频率范围内。输出信号VOUT传输到超声波换能器，激励超声波换能器产生超声波信号。由于超声波信号具有良好的方向性，紫外光信号接收器将接收到受调制的超声波信号。然后，紫外光信号接收器再通过超声波换能器将超声波信号还原为电学信号。紫外光信号接收器会解码所得到的电学信号，判断所接收信号中是否含有紫外光照射的信息，如果含有紫外光照射信息，则执行报警操作。此外，还可以通过信号的频率和强度折算得到紫外光照射的强度等信息。
在一种实施方式中，可以在一定范围内布置若干个紫外光传感节点，紫外光传感节点包括紫外光感应电路和紫外光信号发射器，它们共用一个紫外光信号接收器。于是，可以根据紫外光传感节点的位置计算得到紫外光线的地理位置。这种紫外光传感系统可以布置在山林中，作为山火预警系统；也可以放在矿井中，作为瓦斯爆炸预警；布置在加油站等 易燃易爆场所，作为火灾或者爆炸预警。
本实施例中的紫外光传感系统具有以下优点：
1)由于紫外光敏感器件以及信号调制电路全部采用氧化物TFT构成，而氧化物TFT具有制备成本低廉，便于大面积生产，因此整套的紫外光传感系统的价格低廉；
2)该紫外光传感系统能够输出幅度调制波，适合于较远距离的无线通信；
3)对紫外光的灵敏度高，可以通过其输出脉冲的强度和频率等信息准确地判断其外界的紫外光情况；
4)系统配置灵活、适用范围广，紫外光传感器节点和紫外光信号接收器可以分布在较宽的物理位置上。
以上应用了具体个例对本发明进行阐述，只是用于帮助理解本发明并不用以限制本发明。对于本领域的一般技术人员，依据本发明的思想，可以对上述具体实施方式进行变化。

Claims (11)

  1. 一种紫外光传感电路，其特征在于，包括调制单元和相位延迟单元；
    所述调制单元包括第一级反相器，用于感应紫外光并作为电压反馈调制级；
    所述相位延迟单元包括顺次连接的N级反相器，N为大于等于2的偶数；
    所述调制单元和所述相位延迟单元顺序连接，所述相位延迟单元的输出电压馈送至所述调制单元；
    所述调制单元受控制信号调制，所述控制信号为脉冲信号。
  2. 如权利要求1所述的紫外光传感电路，其特征在于，还包括输出缓冲单元，所述输出缓冲单元包括第N+2级反相器，所述输出缓冲单元提高所述紫外光传感电路对输出端负载的驱动能力。
  3. 如权利要求2所述的紫外光传感电路，其特征在于，所述第一级反相器包括上拉模块和下拉模块；
    所述上拉模块包括第一晶体管和第二晶体管，所述第一晶体管的控制极和第一电极耦合至所述控制信号；所述第二晶体管的控制极耦合至所述第一晶体管的第二电极，所述第二晶体管的第一电极耦合至所述控制信号；
    所述下拉模块包括第三晶体管、第四晶体管、第五晶体管和第六晶体管，所述第三晶体管的控制极耦合到第二电极，第一电极耦合至所述第一晶体管的第二电极；所述第四晶体管的控制极耦合到第二电极，第一电极耦合至所述第二晶体管的第二电极；所述第五晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第三晶体管的第二电极，第二电极耦合至低电平电压源；所述第六晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第四晶体管的第二电极，第二电极耦合至低电平电压源；
    所述第三晶体管和所述第四晶体管为紫外光敏感晶体管。
  4. 如权利要求3所述的紫外光传感电路，其特征在于，所述N级反相器中每一级反相器的电路结构相同，包括第七晶体管、第八晶体管、第九晶体管和第十晶体管；
    所述第七晶体管的控制极和第一电极耦合至所述控制信号；所述第八晶体管的控制极耦合至所述第七晶体管的第二电极，所述第八晶体管的第一电极耦合至所述控制信号；所述第九晶体管的控制极耦合至所述第二晶体管的第二电极，第一电极耦合至所述第七晶体管的第二电极，第二电极耦合至低电平电压源；所述第十晶体管的控制极耦合至所述第九晶体管的控制极，第一电极耦合至所述第八晶体管的第二电极，第二 电极耦合至低电平电压源。
  5. 如权利要求4所述的紫外光传感电路，其特征在于，所述第九晶体管和所述第十晶体管为紫外光敏感晶体管。
  6. 如权利要求2所述的紫外光传感电路，其特征在于，所述第一级反相器包括上拉模块和下拉模块；
    所述上拉模块包括第一晶体管和第二晶体管，所述第一晶体管的控制极和第一电极耦合至所述控制信号；所述第二晶体管的控制极耦合至所述第一晶体管的第二电极，所述第二晶体管的第一电极耦合至所述控制信号；
    所述下拉模块包括第三晶体管、第四晶体管、第五晶体管和第六晶体管，所述第三晶体管的控制极耦合至第一控制信号，第一电极耦合至所述第一晶体管的第二电极；所述第四晶体管的控制极耦合至所述第一控制信号，第一电极耦合至所述第二晶体管的第二电极；所述第五晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第三晶体管的第二电极，第二电极耦合至低电平电压源；所述第六晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第四晶体管的第二电极，第二电极耦合至低电平电压源；
    所述第三晶体管和所述第四晶体管为紫外光敏感晶体管。
  7. 如权利要求2所述的紫外光传感电路，其特征在于，所述第一级反相器包括上拉模块和下拉模块；
    所述上拉模块包括第一晶体管和第二晶体管，所述第一晶体管的控制极和第一电极耦合至高电平信号；所述第二晶体管的控制极耦合至所述第一晶体管的第二电极，所述第二晶体管的第一电极耦合至所述高电平信号；
    所述下拉模块包括第三晶体管、第四晶体管、第五晶体管、第六晶体管和第十五晶体管，所述第三晶体管的控制极耦合至所述控制信号，第一电极耦合至所述第一晶体管的第二电极；所述第四晶体管的控制极耦合至所述控制信号，第一电极耦合至所述第二晶体管的第二电极；所述第五晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第三晶体管的第二电极；所述第六晶体管的控制极耦合至所述N级反相器的输出端，第一电极耦合至所述第四晶体管的第二电极；所述第十五晶体管的第一电极分别耦合至所述第五晶体管的第二电极和所述第六晶体管的第二电极，所述第十五晶体管的控制极和第二电极耦合至低电平电压源，所述第十五晶体管为紫外光敏感晶体管。
  8. 如权利要求2所述的紫外光传感电路，其特征在于，所述第N+2级反相器包括第十一晶体管、第十二晶体管、第十三晶体管和第十四晶体管；
    所述第十一晶体管的控制极和第一电极耦合至所述控制信号；所述第十二晶体管的控制极耦合至所述第十一晶体管的第二电极，所述第十二晶体管的第一电极耦合至所述控制信号，所述第十二晶体管的第二电极耦合至输出端；所述第十三晶体管的控制极耦合至所述N级反相器的输出端，所述第十三晶体管的第一电极耦合至所述第十一晶体管的第二电极，所述第十三晶体管的第二电极耦合至低电平电压源；所述第十四晶体管的控制极耦合至所述N级反相器的输出端，所述第十四晶体管的第一电极耦合至所述第十二晶体管的第二电极，所述第十三晶体管的第二电极耦合至低电平电压源。
  9. 如权利要求3、5、6或7中任一项所述的紫外光传感电路，其特征在于，所述紫外光敏感晶体管为锌基氧化物薄膜晶体管。
  10. 一种紫外光感应系统，其特征在于，包括紫外光信号发射器、紫外光信号接收器和如权利要求1-9中任一项所述的紫外光传感电路；
    所述紫外光传感电路的输出端耦合至所述紫外光信号发射器，所述紫外光信号发射器用于发射紫外光传感电路输送的信号，所述紫外光信号接收器用于接收所述紫外光信号发射器传送的信号，并根据接收到的信号判断所述紫外光传感电路是否存在紫外光照射。
  11. 如权利要求10所述的紫外光感应系统，其特征在于，所述紫外光信号发射器为超声波换能器，用于在所述紫外光传感电路的输出电压信号的激励下产生超声波信号并发射所述超声波信号；所述紫外光信号接收器接收所述超声波信号，将所述超声波信号还原成电信号，并根据所述电信号判断所述紫外光传感电路是否存在紫外光照射。
PCT/CN2014/091061 2014-03-05 2014-11-14 一种紫外光传感电路及感应系统 Ceased WO2015131545A1 (zh)

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