Gas sensor module

Abstract

To provide a gas sensor module capable of reducing a load applied to a power source.SOLUTION: A gas sensor module 100 includes: an infrared light emitting diode 10 for emitting infrared light according to a drive current; a quantum infrared sensor 20 for receiving infrared light that has passed through gas to be detected; a drive circuit 30 for outputting a drive current to the infrared light emitting diode 10; a charging circuit 50 that is connected to a power source and outputs a charging current smaller in amount of current than the drive current; and a capacitor 40 that is charged by being supplied with the charging current from the charging circuit 50 and discharges by supplying the drive current to the drive circuit 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a gas sensor module. [Background technology]

[0002] Conventionally, a method for driving a light source for a CO2 gas sensor is known in which the voltage of an incandescent lamp used in a CO2 gas sensor is controlled so that the filament resistance value in the lit state is constant (see, for example, Patent Document 1).

[0003] In recent years, development has been progressing on non-dispersive infrared (NDIR) gas sensors, which include a light-emitting element that emits infrared rays and a light-receiving element that receives infrared rays that have passed through a gas to be detected (e.g., CO2 gas), and which detect the concentration of the gas by utilizing the infrared absorption characteristics of the gas. [Prior art documents] [Non-patent literature]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-215990 Summary of the Invention [Problem to be solved by the invention]

[0005] Non-dispersive infrared absorption gas sensors have an extremely large drive current (peak current) compared to other environmental sensors such as temperature and humidity sensors, pressure sensors, etc. For this reason, in a conventional gas sensor module 100A as shown in Fig. 7, which includes a light-emitting unit 10A such as a tungsten lamp (incandescent lamp) or MEMS heater and a light-receiving unit 20A such as a pyroelectric sensor or thermopile, there was a problem of excessive load being placed on the power supply 60A.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a gas sensor module that can reduce the load on a power supply. [Means for solving the problem]

[0007] A gas sensor module according to one embodiment comprises an infrared emitting diode that emits infrared light in response to a drive current, a quantum infrared sensor that receives infrared light that has passed through a gas to be detected, a drive circuit that outputs the drive current to the infrared emitting diode, a charging circuit that is connected to a power source and outputs a charging current that is smaller in magnitude than the drive current, and a capacitor that is charged by the charging current supplied from the charging circuit and discharges by supplying the drive current to the drive circuit. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a gas sensor module that can reduce the load on a power supply. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a configuration of a gas sensor module according to an embodiment of the present invention. [Figure 2A] FIG. 4 is a diagram showing an example of the response of the infrared light emitting diode according to the embodiment. [Figure 2B] FIG. 10 is a diagram illustrating an example of the response of a conventional light-emitting unit. [Figure 2C] FIG. 10 is a diagram illustrating an example of the response of a conventional light-emitting unit. [Figure 3A] 1 is a diagram showing an example of the sensitivity of the quantum infrared sensor according to the embodiment and the sensitivity of a conventional light receiving unit; [Figure 3B] 10A and 10B are diagrams illustrating an example of noise equivalent power of the quantum infrared sensor according to the present embodiment and noise equivalent power of a conventional light receiving unit. [Figure 4] 10 is a diagram showing an example of the relationship between a voltage drop of a power supply due to discharge of a capacitor and the capacitance of the capacitor; [Figure 5A] 1A and 1B are diagrams illustrating a gas sensor module according to an embodiment of the present invention; [Figure 5B]1A and 1B are diagrams illustrating a gas sensor module according to an embodiment of the present invention; [Figure 5C] 1A and 1B are diagrams illustrating a gas sensor module according to an embodiment of the present invention; [Figure 6] FIG. 10 is a diagram illustrating a conventional gas sensor module. [Figure 7] FIG. 1 is a diagram showing an example of the configuration of a conventional gas sensor module. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0011] An example of the configuration of a gas sensor module 100 according to this embodiment will be described with reference to FIGS.

[0012] As shown in FIG. 1, the gas sensor module 100 includes an infrared emitting diode 10, a quantum infrared sensor 20, a driving circuit 30, a capacitor 40, a charging circuit 50, a power supply 60, and an amplifier circuit / signal processing circuit 70.

[0013] The infrared light emitting diode 10 is driven by a driving current I drive The infrared light emitting diode 10 emits infrared light in response to the infrared light. The infrared light emitting diode 10 is used as a light source for sensing a detection target gas (for example, CO2 gas) that has infrared absorption properties. The infrared light emitting diode 10 preferably emits light in the wavelength range of 2.0 μm to 12.0 μm.

[0014] The infrared light emitting diode 10 is preferably configured as a light source with good response.

[0015] Here, referring to FIGS. 2A to 2C, the responsiveness of the infrared light-emitting diode 10 according to the present embodiment and the responsiveness of the conventional light-emitting unit will be described. FIG. 2A is a diagram showing an example of the responsiveness of an infrared light-emitting diode. FIG. 2B is a diagram showing an example of the responsiveness of a tungsten lamp. FIG. 2C is a diagram showing an example of the responsiveness of a MEMS (Micro Electro Mechanical Systems) heater. Here, a quantum infrared sensor with good responsiveness is used as the light-receiving unit so that detection signals depending on the responsiveness of each light-emitting unit can be obtained.

[0016] In FIG. 2A, graph 201 shows the drive voltage of the infrared light-emitting diode 10. Graph 202 shows the drive current of the infrared light-emitting diode 10. Graph 203 shows the detection signal of the light-receiving unit.

[0017] In FIGS. 2B and 2C, graph 201 shows the drive voltage of the conventional light-emitting unit. Graph 202 shows the drive current of the conventional light-emitting unit. Graph 203 shows the detection signal of the light-receiving unit.

[0018] From graph 203 in FIG. 2A, it can be seen that when an infrared light-emitting diode is used, the time constant of the detection signal is about several μs (<< ms). From graph 203 in FIG. 2B, it can be seen that when a tungsten lamp is used, the time constant of the detection signal is about 50 ms. From graph 203 in FIG. 2C, it can be seen that when a MEMS heater is used, the time constant of the detection signal is about 30 ms.

[0019] 2A, it can be seen that the time from when the drive current is supplied to the infrared light-emitting diode until the detection signal reaches its peak value is very short, and the peak is reached immediately after the drive current starts to be supplied. Graphs 201, 202, and 203 in FIG. 2B also show that the time from when the drive current is supplied to the tungsten lamp until the detection signal reaches its peak value is approximately 100 ms or more. Graphs 201, 202, and 203 in FIG. 2C also show that the time from when the drive current is supplied to the MEMS heater until the detection signal reaches its peak value is approximately 100 ms or more.

[0020] 2A to 2C show that infrared light-emitting diodes have significantly better response than tungsten lamps or MEMS heaters. This suggests that infrared light-emitting diodes can achieve significantly shorter drive times per cycle than tungsten lamps or MEMS heaters. For example, the drive time can be reduced to 1 ms or less. An even shorter range is possible, approximately 10 μs to 100 μs. The on-duty ratio of the drive current (the ratio of the time the drive current flows to the drive cycle) can also be reduced, for example, to 10% or less. This reduces the load on the power supply while achieving low power consumption for the gas sensor module. While the light output of visible light-emitting diodes is important, the gas sensor module only requires a drive time that provides the required signal-to-noise ratio. Furthermore, the gas concentration monitoring cycle is generally sufficient, typically on the order of seconds, allowing for a relatively long drive cycle.

[0021] The quantum infrared sensor 20 receives infrared light that has passed through the target gas. The quantum infrared sensor 20 detects the amount of absorption of the target gas, which has infrared absorption properties, according to the amount of infrared light received, and outputs a detection signal indicating the concentration of the target gas to the amplifier circuit / signal processing circuit 70. The higher the concentration of the target gas, the smaller the amount of infrared light received by the quantum infrared sensor 20. The lower the concentration of the target gas, the larger the amount of infrared light received by the quantum infrared sensor 20. Note that the distance between the quantum infrared sensor 20 and the infrared emitting diode 10 is preferably about 20 mm, but is not limited to this.

[0022] The gas to be detected is preferably a gas species that has absorption characteristics for light in the wavelength range of 2.0 μm to 12.0 μm, and examples thereof include, but are not limited to, CO2, CO, CH4, H2O, NO, C2H5OH, C3H8, NH3, and CHO.

[0023] The quantum infrared sensor 20 may further include an optical filter that transmits light of a certain wavelength. An example of an optical filter is a bandpass filter that transmits light in the absorption wavelength band of the target gas. For example, when detecting carbon dioxide, a bandpass filter that selectively transmits light around 4.3 μm may be used.

[0024] The quantum infrared sensor 20 is preferably mounted on the same substrate as the infrared emitting diode 10. Mounting the quantum infrared sensor 20 and the infrared emitting diode 10 on the same substrate eliminates the need to prepare separate substrates, thereby reducing manufacturing costs. Furthermore, mounting the quantum infrared sensor 20 and the infrared emitting diode 10 on the same substrate improves detection accuracy.

[0025] The quantum infrared sensor 20 is preferably configured with an element that has high sensitivity and low noise. Examples of quantum infrared sensors include a phototube, a photodiode, and a phototransistor.

[0026] Here, the sensitivity and noise equivalent power of the quantum infrared sensor 20 according to this embodiment, as well as the sensitivity and noise equivalent power of a conventional light receiving unit, will be described with reference to Figures 3A and 3B. Figure 3A is a diagram showing an example of the relationship between frequency and sensitivity. The horizontal axis represents frequency [Hz], and the vertical axis represents sensitivity [V rms / W rms ]. FIG. 3B is a diagram showing an example of the relationship between frequency and noise equivalent power. The horizontal axis is frequency [Hz], and the vertical axis is noise equivalent power [W rms / rtHz].

[0027] Graph 301A in Fig. 3A shows the sensitivity of a quantum infrared sensor, graph 302A in Fig. 3A shows the sensitivity of a thermopile, and graph 303A in Fig. 3A shows the sensitivity of a pyroelectric sensor.

[0028] Graph 301B in Fig. 3B shows the noise equivalent power of a quantum infrared sensor, graph 302B in Fig. 3B shows the noise equivalent power of a thermopile, and graph 303B in Fig. 3B shows the noise equivalent power of a pyroelectric sensor.

[0029] Graph 301A in Fig. 3A shows that the sensitivity of the quantum infrared sensor is generally high and remains approximately constant even when the frequency changes. Graph 302A in Fig. 3A shows that the sensitivity of the thermopile is generally low and remains approximately constant up to a frequency of 10 Hz, but drops sharply when the frequency exceeds 10 Hz. Graph 303A in Fig. 3A shows that the sensitivity of the pyroelectric sensor decreases as the frequency increases.

[0030] Graph 301B in Fig. 3B shows that the noise equivalent power of the quantum infrared sensor is generally small and remains approximately constant even when the frequency changes. Graph 302B in Fig. 3B shows that the noise equivalent power of the thermopile is generally large and remains approximately constant up to a frequency of 10 Hz, but rises sharply when the frequency exceeds 10 Hz. Graph 303B in Fig. 3B shows that the noise equivalent power of the pyroelectric sensor is generally large and increases as the frequency increases.

[0031] 3A and 3B, it can be seen that the quantum infrared sensor has higher sensitivity and stability compared to the thermopile or pyroelectric sensor. It can also be seen that the quantum infrared sensor has lower noise and is more stable compared to the thermopile or pyroelectric sensor.

[0032] Therefore, it is suggested that when an infrared emitting diode is combined with a quantum infrared sensor, the driving time per cycle of the infrared emitting diode 10 can be made extremely short compared to when a tungsten lamp or MEMS heater is combined with a thermopile or pyroelectric sensor. For example, the driving time can be made 1 ms or less.

[0033] From the viewpoint of sufficiently charging the capacitor 40, it is preferable that the product of the charging current and the charging time be equal to or greater than the product of the driving current and the driving time.

[0034] The drive circuit 30 is provided between the infrared light emitting diode 10 and the capacitor 40. The drive circuit 30 is connected to the capacitor 40 via a switch SW2, and is also connected to the infrared light emitting diode 10. When the capacitor 40 is discharged, the drive circuit 30 supplies a drive current I drive Then, the driving circuit 30 supplies the driving current I drive The driving current I of the infrared light emitting diode 10 is supplied. drive The driving current I of the infrared light emitting diode 10 is preferably about 100 mA. driveThe larger the value, the greater the amount of light emitted by the infrared light emitting diode 10, and the better the signal-to-noise ratio can be.

[0035] The capacitor 40 is provided between the charging circuit 50 and the drive circuit 30. The capacitor 40 is connected to the charging circuit 50 via a switch SW1, and is also connected to the drive circuit 30 via a switch SW2. When the switch SW1 is turned on, the capacitor 40 is charged by the charging circuit 50, the capacitor voltage of the capacitor 40 rises, and a charging current I of the capacitor 40 flows between the power supply 60 and the capacitor 40. charge When the switch SW1 is turned off, a charging current I charge When the switch SW2 is turned on, the capacitor 40 does not supply the driving current I drive The capacitor voltage of the capacitor 40 drops, and the driving current I of the infrared light emitting diode 10 flows between the capacitor 40 and the infrared light emitting diode 10. drive When the switch SW2 is turned off, a driving current I drive The switches SW1 and SW2 are not turned on at the same time, and when the switch SW1 is on, the switch SW2 is turned off, and when the switch SW2 is on, the switch SW1 is turned off.

[0036] Charging current I of capacitor 40 charge is the driving current I of the infrared light emitting diode 10 drive From the viewpoint of reducing power consumption and improving measurement accuracy, the charging current I charge is preferably the current obtained by averaging the drive current. charge is the driving current I of the infrared light emitting diode 10 drive For example, when the detection period of the non-dispersive infrared absorption gas sensor is set to 10 seconds, the driving current I of the infrared light emitting diode 10 is preferably about 1 / 100 of the driveis the current that flows instantaneously between the capacitor 40 and the infrared emitting diode 10 at 100 mA for 0.1 ms, 1000 times, and the charging current I charge is the current flowing periodically between power supply 60 and capacitor 40 at 1.01 mA for 9.9 s.

[0037] The driving current I of the infrared light emitting diode 10 is supplied from the charging circuit 50 to the capacitor 40. drive The charging current I of the capacitor 40 is smaller than charge The capacitor 40 is charged by the supply of the current I drive As a result, in the gas sensor module 100, the drive circuit 30 directly supplies the drive current I drive Since there is no need to take out a power supply 60, the load on the power supply 60 can be significantly reduced. That is, when the power supply 60 and the drive circuit 30 are connected via the charging circuit 50, the switch SW1, the capacitor 40, and the switch SW2, as in the gas sensor module 100 according to this embodiment, the load on the power supply 60 can be significantly reduced compared to when the power supply 60A and the drive circuit 30A are directly connected, as in the conventional gas sensor module 100A (see FIG. 7). Furthermore, the light emission amount of the infrared light emitting diode 10 can be maintained at the same level as the light emission amount of the light emitting unit 10A of a tungsten lamp or a MEMS heater.

[0038] The capacitor 40 is preferably configured with an element having a low capacitance, for example, a multilayer ceramic capacitor from the viewpoints of size, cost, and leakage current. The capacitor 40 preferably has a capacitance of 1 mF or less.

[0039] Here, the relationship between the voltage drop caused by discharging the capacitor and the capacitance of the capacitor will be described with reference to Fig. 4. The horizontal axis represents the voltage drop ΔV [mV], and the vertical axis represents the capacitance C of the capacitor. bulk [F].

[0040] Graph 401 in Fig. 4 shows the capacitance of the capacitor when an infrared light emitting diode is used in the gas sensor module, i.e., when the driving time of the infrared light emitting diode per drive is 100 μs. Graph 402 in Fig. 4 shows the capacitance of the capacitor when a tungsten lamp or MEMS heater is used in the gas sensor module, i.e., when the driving time of the tungsten lamp or MEMS heater per drive is 100 ms. In Fig. 4, the driving current of the infrared light emitting diode and the driving current of the tungsten lamp or MEMS heater are both 100 mA.

[0041] From the graph 401 in FIG. 4, the larger the voltage drop ΔV, the larger the capacitance C bulk For example, if the voltage drop ΔV is 1 mV, the capacitance C of the capacitor bulk is 10mF, and if the voltage drop ΔV is 100mV, the capacitance of the capacitor C bulk is found to be 100μF.

[0042] From the graph 402 in FIG. 4, the larger the voltage drop ΔV, the larger the capacitance C bulk For example, if the voltage drop ΔV is 1 mV, the capacitance C of the capacitor bulk is 10F, and if the voltage drop ΔV is 100mV, the capacitance of the capacitor C bulk is found to be 100mF.

[0043] As can be seen from Figure 4, the larger the allowable voltage drop ΔV, the larger the required capacitor capacitance C bulk It can be seen that the capacitance of the capacitor when an infrared light-emitting diode is used in a gas sensor module can be made much smaller than the capacitance of the capacitor when a tungsten lamp or MEMS heater is used in a gas sensor module.

[0044] When an infrared light-emitting diode is used in a gas sensor module, an example of the capacitor is a multilayer ceramic capacitor. Multilayer ceramic capacitors often have a capacitance on the order of μF, are small in size, are inexpensive, and have almost no leakage current. On the other hand, when a tungsten lamp or a MEMS heater is used in a gas sensor module, an example of the capacitor is an electric double layer capacitor. Electric double layer capacitors often have a capacitance on the order of mF, are large in size, are expensive, and have a leakage current on the order of μA.

[0045] That is, by providing the gas sensor module 100 with a non-dispersive infrared absorption gas sensor that combines an infrared emitting diode and a quantum infrared sensor, the driving time of the infrared emitting diode 10 can be made extremely short, and therefore the capacitance of the capacitor 40 can be made extremely small. This makes it possible to reduce the size and cost of not only the capacitor 40 but also the entire gas sensor module 100.

[0046] The charging circuit 50 is provided between the power supply 60 and the capacitor 40. The charging circuit 50 is connected to the power supply 60 and also connected to the capacitor 40 via the switch SW1. The charging circuit 50 receives a driving current I drive The charging current I of the capacitor 40 is smaller than charge Then, the charging circuit 50 supplies the charging current I charge The charging current I of the capacitor 40 is supplied. charge For example, if the detection cycle of the non-dispersive infrared absorption gas sensor is 10 seconds, the charging circuit 50 periodically supplies a current of 1.01 mA to the capacitor 40 for 9.9 seconds, while the driving circuit 30 instantaneously supplies a current of 100 mA to the infrared emitting diode 10 1,000 times for 0.1 ms.

[0047] The charging circuit 50 is not particularly limited as long as it is a charging means having a current supply capacity that is sufficiently low, for example, about 1 / 100, compared to the drive circuit 30. Examples of the charging circuit 50 include a resistor, a current source, a DC-DC converter, and a charge pump.

[0048] The charging circuit 50 and the capacitor 40 supply the driving current I drive By having the function of averaging, it is possible to significantly reduce the load on the power supply 60 while maintaining the light emission amount of the infrared light emitting diode 10 at the same level as the light emission amount of the light emitting unit 10A.

[0049] <Timing chart> 5A to 5C, 6, and 7, the differences between the gas sensor module 100 according to this embodiment and the conventional gas sensor module 100A will be described below. The following describes an example in which the detection period of the non-dispersive infrared absorption gas sensor is set to 10 seconds.

[0050] [Gas sensor module 100 according to this embodiment] 5A, the state of the infrared light emitting diode 10 in the gas sensor module 100 according to this embodiment, the driving current I drive , the capacitor voltage V of the capacitor 40 c , the charging current I of the capacitor 40 charge The state of the drive circuit 30 and the state of the amplifier circuit / signal processing circuit 70 will be described.

[0051] The infrared emitting diode 10 repeatedly maintains a non-emitting state, switches from the non-emitting state to the emitting state, maintains the emitting state, and switches from the emitting state to the non-emitting state. The infrared emitting diode 10 emits light 1,000 times in a detection cycle of 10 seconds. The driving time of the infrared emitting diode 10 per light emission is 100 μs. The non-driving time of the infrared emitting diode 10 per light emission is 9,900 μs.

[0052] The driving current I of the infrared light emitting diode 10drive The driving current I of the infrared light emitting diode 10 is maintained at 0 mA, switched from 0 mA to 100 mA, maintained at 100 mA, and switched from 100 mA to 0 mA. drive When the driving current I of the infrared emitting diode 10 is kept at 0 mA, the state of the infrared emitting diode 10 is kept at the non-emitting state. drive When the driving current I of the infrared emitting diode 10 is switched from 0 mA to 100 mA, the state of the infrared emitting diode 10 is switched from a non-emitting state to an emitting state. drive When the driving current I of the infrared emitting diode 10 is maintained at 100 mA, the state of the infrared emitting diode 10 is maintained in the light emitting state. drive When the current switches from 100 mA to 0 mA, the state of the infrared emitting diode 10 switches from an emitting state to a non-emitting state.

[0053] The drive circuit 30 repeatedly maintains the off state, switches from the off state to the on state, maintains the on state, and switches from the on state to the off state. The drive circuit 30 is turned on and off 1,000 times in a detection cycle of 10 seconds. The on-time of the drive circuit 30 per cycle is 100 μs. The off-time of the drive circuit 30 per cycle is 9,900 μs. The duty cycle is expressed as [on-time of the drive circuit 30 per cycle × number of on-off cycles of the drive circuit 30] / [detection cycle of the non-dispersive infrared absorption gas sensor], so for example, duty cycle = (100 μs × 1,000) / 10 seconds = 1%. When the drive circuit 30 maintains the off state, the infrared-emitting diode 10 maintains a non-emitting state. When the drive circuit 30 switches from an off state to an on state, the infrared-emitting diode 10 switches from a non-emitting state to an emitting state. When the driving circuit 30 maintains the on state, the infrared emitting diode 10 maintains the light emitting state. When the driving circuit 30 switches from the on state to the off state, the infrared emitting diode 10 switches from the light emitting state to the non-light emitting state.

[0054] Capacitor voltage V of capacitor 40 cWhen the switch SW1 is turned on (see FIGS. 5B and 5C), a charging current I of the capacitor 40 flows between the power supply 60 and the capacitor 40. charge flows, and the capacitor 40 is charged, resulting in a capacitor voltage V c In this case, the infrared emitting diode 10 maintains its non-light emitting state. When the switch SW2 is turned on (see FIGS. 5B and 5C), a driving current I for the infrared emitting diode 10 flows between the capacitor 40 and the driving circuit 30. drive flows, and the capacitor 40 is discharged, resulting in the capacitor voltage V c In this case, the state of the infrared emitting diode 10 remains in the light emitting state.

[0055] Charging current I of capacitor 40 charge is equal to the current of the power supply 60. The charging current I of the capacitor 40 charge is the driving current I of the infrared light emitting diode 10 drive The required current is smaller than the driving current I of the infrared light emitting diode 10. drive × ON time / OFF time], so for example, the charging current I charge = (100mA × (100μs × 1000) / (9900μA × 1000)) = 1.01mA. That is, the charging current I charge is the driving current I of the infrared light emitting diode 10 drive As is clear from FIG. 5A, the driving current I drive is the current that flows instantaneously between the capacitor 40 and the infrared emitting diode 10 at 100 mA for 0.1 ms, 1000 times, during a detection period of 10 seconds. The charging current I charge is a current that periodically flows between the power supply 60 and the capacitor 40 at 1.01 mA for 9.9 seconds during a detection period of 10 seconds. That is, the charging circuit 50 and the capacitor 40 are configured to supply the driving current I driveBy having the function of averaging the charging current I, it is possible to significantly reduce the load on the power supply 60 while maintaining the light emission amount of the infrared light emitting diode 10 at the same level as the light emission amount of the light emitting unit 10A. charge is sufficient to complete charging of the capacitor 40 within the time limit, and therefore, it is sufficient to have a current greater than 1.01 mA. For example, it may be 2 mA.

[0056] The amplifier circuit / signal processing circuit 70 repeatedly maintains the off state, switches from the off state to the on state, maintains the on state, and switches from the on state to the off state. The amplifier circuit / signal processing circuit 70 is turned on and off 1000 times in a detection cycle of 10 seconds. The on time of the amplifier circuit / signal processing circuit 70 per turn is 100 μs. The off time of the amplifier circuit / signal processing circuit 70 per turn is 9900 μs. When the amplifier circuit / signal processing circuit 70 switches from the on state to the off state for the 1000th time, a detection signal is output from the quantum infrared sensor 20 to the amplifier circuit / signal processing circuit 70.

[0057] Next, referring to FIGS. 5B and 5C, the capacitor voltage V of the capacitor 40 c and the capacitor voltage V of the capacitor 40 c Details will be explained below.

[0058] When the switch SW2 is turned on, the capacitor 40 and the drive circuit 30 are connected, and the drive current I of the infrared light emitting diode 10 flows between the capacitor 40 and the infrared light emitting diode 10. drive In this case, the capacitor voltage V of the capacitor 40 c decreases, and the capacitor 40 supplies the driving current I drive By supplying a voltage Vcc, the capacitor 40 is discharged.

[0059] When the switch SW2 is switched to the switch SW1, the voltage drop ΔV of the capacitor voltage Vc caused by the discharge of the capacitor 40 is dd and the capacitor voltage V of capacitor 40 cThe minimum value of V cmin Since it is the difference between these, it is expressed by the following equation: Considering the reduction in power consumption of the gas sensor module 100, it is preferable that the voltage drop ΔV of the capacitor voltage Vc caused by the discharge of the capacitor 40 is about several hundred mV.

[0060]

number

[0061] When the switch SW1 is turned on, the charging circuit 50 and the capacitor 40 are connected, and a charging current I charge In this case, the capacitor voltage V of the capacitor 40 c rises, and the charging current I charge is supplied, the capacitor 40 is charged.

[0062] Here, the capacitor voltage V of the capacitor 40 c is required to satisfy the following equation:

[0063]

number

[0064] Furthermore, the voltage drop ΔV of the capacitor voltage Vc must satisfy the following equation:

[0065]

number

[0066] Therefore, the capacitance C of the capacitor 40 bulk The voltage drop ΔV of the capacitor voltage Vc is dd from the driving voltage V of the infrared light emitting diode 10emitter and the voltage V required for the drive circuit 30 to operate normally. ds The capacitance C of the capacitor 40 is selected to be smaller than the sum of bulk is expressed by the following equation:

[0067]

number

[0068] From equation (4), the capacitance C of the capacitor 40 bulk is the driving time t of the infrared emitting diode 10 per one time. ON That is, the shorter the driving time of the infrared light emitting diode 10 per one time, the smaller the capacitance C of the capacitor 40. bulk It can be seen that it is possible to reduce

[0069] In other words, the gas sensor module 100 includes a non-dispersive infrared absorption gas sensor in which an infrared emitting diode and a quantum infrared sensor are combined, so that the driving time t ON Since the capacitance C of the capacitor 40 can be made extremely short, bulk It can be seen that the

[0070] [Conventional gas sensor module 100A] 6 and 7, the state of the light emitting unit 10A in the conventional gas sensor module 100A, the driving current I drive The state of the drive circuit 30A and the state of the amplifier circuit / signal processing circuit 70A will be described.

[0071] The light-emitting unit 10A repeats the cycle of maintaining a non-light-emitting state, switching from the non-light-emitting state to the light-emitting state, maintaining the light-emitting state, and switching from the light-emitting state to the non-light-emitting state. The light-emitting unit 10A emits light once in a detection cycle of 10 seconds. The driving time of the light-emitting unit 10A per one cycle is 0.1 seconds. The non-driving time of the light-emitting unit 10A per one cycle is 9.9 seconds.

[0072] Driving current I of light-emitting unit 10A drive is equal to the current of the power supply 60A. The driving current I drive The driving current I of the light-emitting unit 10A is maintained at 0 mA, switched from 0 mA to 100 mA, maintained at 100 mA, and switched from 100 mA to 0 mA. drive When the driving current I of the light-emitting unit 10A is maintained at 0 mA, the light-emitting unit 10A is maintained in the non-light-emitting state. drive When the driving current I of the light-emitting unit 10A is switched from 0 mA to 100 mA, the state of the light-emitting unit 10A is switched from a non-light-emitting state to a light-emitting state. drive When the driving current I of the light-emitting unit 10A is maintained at 100 mA, the state of the light-emitting unit 10A is maintained in the light-emitting state. drive When the current flows from 100 mA to 0 mA, the state of the light-emitting unit 10A switches from the light-emitting state to the non-light-emitting state.

[0073] The drive circuit 30A repeatedly maintains the off state, switches from the off state to the on state, maintains the on state, and switches from the on state to the off state. The drive circuit 30A is turned on and off once per 10-second detection cycle. The on-time of the drive circuit 30A per cycle is 0.1 seconds. The off-time of the drive circuit 30A per cycle is 9.9 seconds. The duty cycle is expressed as [on-time of the drive circuit 30A per cycle × number of on-off cycles of the drive circuit 30A] / [detection cycle of the non-dispersive infrared absorption gas sensor], so for example, duty cycle = (0.1 seconds × 1) / 10 seconds = 1%. When the drive circuit 30A maintains the off state, the light-emitting unit 10A maintains the non-light-emitting state. When the drive circuit 30A switches from the off state to the on state, the light-emitting unit 10A switches from the non-light-emitting state to the light-emitting state. When the drive circuit 30A maintains the ON state, the light-emitting unit 10A maintains the emitting state. When the drive circuit 30A switches from the ON state to the OFF state, the light-emitting unit 10A switches from the emitting state to the non-emitting state.

[0074] The amplifier circuit / signal processing circuit 70A repeatedly maintains the off state, switches from the off state to the on state, maintains the on state, and switches from the on state to the off state. The amplifier circuit / signal processing circuit 70A is turned on and off once per 10-second detection period. The on-time of each amplifier circuit / signal processing circuit 70A is 0.1 seconds. The off-time of each amplifier circuit / signal processing circuit 70A is 9.9 seconds. When the amplifier circuit / signal processing circuit 70A switches from the on state to the off state for the first time, a detection signal is output from the light receiving unit 20A, such as a pyroelectric sensor or thermopile, to the amplifier circuit / signal processing circuit 70A.

[0075] [Comparison] As described above, it can be seen that the driving time per cycle of the infrared light emitting diode 10 is 1 / 1000 of the driving time per cycle of the light emitting unit 10A. In other words, it can be seen that the gas sensor module 100 according to this embodiment can significantly shorten the driving time per cycle of the infrared light emitting diode compared to the conventional gas sensor module 100A.

[0076] It is also seen that the peak current of the power supply 60 is 1 / 100 of the peak current of the power supply 60 A. In other words, it is seen that the gas sensor module 100 according to this embodiment can significantly reduce the load on the power supply compared to the conventional gas sensor module 100 A.

[0077] It can also be seen that the on-time of the drive circuit 30 per one emission is 1 / 1000 times the on-time of the drive circuit 30A per one emission. That is, compared to the conventional gas sensor module 100A, even if the duty cycle is the same, the gas sensor module 100 according to this embodiment can make the on-time of the drive circuit 30 per one emission of light from the infrared light emitting diode 10 shorter than the on-time of the drive circuit 30A per one emission of light from the light emitting unit 10A per one emission of light, and therefore it can be seen that the load on the power supply can be significantly reduced.

[0078] The gas sensor module 100 according to this embodiment utilizes the periodic emission of the infrared emitting diode 10 included in the non-dispersive infrared absorption gas sensor to generate a driving current I drive The charging circuit 50 charges the capacitor 40 with a current smaller than the current amount I , and the capacitor 40 supplies the driving current I for the infrared emitting diode 10 to the driving circuit 30. drive This makes it possible to significantly reduce the load on the power supply 60 compared to the conventional gas sensor module 100A without changing the amount of light emitted by the infrared emitting diode 10. Furthermore, it is possible to stabilize the operation of the gas sensor module itself without adversely affecting the operation of other devices (e.g., other environmental sensors) mounted on the same board.

[0079] Furthermore, the gas sensor module 100 according to this embodiment includes a non-dispersive infrared absorption gas sensor that combines an infrared emitting diode and a quantum infrared sensor, and therefore the driving time of the infrared emitting diode 10 can be made extremely short compared to a case in which a tungsten lamp or an MEMS heater is combined with a thermopile or a pyroelectric sensor. This allows the capacitance of the capacitor 40 to be made extremely small, thereby enabling the gas sensor module 100 to be made smaller and less expensive overall.

[0080] <Modification> The present invention is not limited to the above-described embodiments and modifications. For example, the various processes described above may not only be executed in chronological order as described, but may also be executed in parallel or individually depending on the processing capabilities of the devices that execute the processes or as needed. Other modifications are possible without departing from the spirit of the present invention.

[0081] Although the above-described embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and alterations are possible without departing from the scope of the claims. For example, multiple building blocks shown in the block diagrams of the embodiments can be combined into one, or one building block can be divided. [Explanation of symbols]

[0082] 10 Infrared light emitting diode 20 Quantum infrared sensor 30 Drive circuit 40 Capacitor 50 Charging circuit 60 power supply 70 Amplification circuit / signal processing circuit 100 Gas Sensor Module 10A Light emitting part 20A light receiving part 30A drive circuit 60A power supply 70A Amplification circuit / signal processing circuit 100A Conventional gas sensor module

Claims

1. an infrared light emitting diode that emits infrared light in response to a drive current; a quantum infrared sensor that receives infrared light that has passed through the gas to be detected; a drive circuit that outputs the drive current to the infrared light emitting diode; a charging circuit connected to a power supply and outputting a charging current smaller in amount than the driving current; a capacitor that is charged by the charging current supplied from the charging circuit and that is discharged by the drive current supplied to the drive circuit; A gas sensor module comprising:

2. the product of the charging current and the charging time is equal to or greater than the product of the driving current and the driving time; The gas sensor module according to claim 1 .

3. The driving time is 1 ms or less.

3. The gas sensor module according to claim 2.

4. the on-duty ratio of the driving current is 10% or less; The gas sensor module according to claim 1 .

5. The capacitor is a multilayer ceramic capacitor. The gas sensor module according to claim 1 .

6. The capacitor has a capacitance of 1 mF or less. The gas sensor module according to claim 1 .

7. a drive circuit for outputting the drive current to an infrared light emitting diode of a non-dispersive infrared absorption gas sensor, the infrared light emitting diode emitting infrared light in response to a drive current and a quantum infrared sensor receiving infrared light transmitted through a gas to be detected; a charging circuit that outputs a charging current having a smaller current amount than the driving current; a capacitor that is charged by the charging current supplied from the charging circuit and that is discharged by the drive current supplied to the drive circuit; 1. A circuit for a gas sensor module comprising:

8. the product of the charging current and the charging time is equal to or greater than the product of the driving current and the driving time; 8. A circuit for a gas sensor module according to claim 7.

9. The driving time is 1 ms or less.

9. A circuit for a gas sensor module according to claim 8.

10. the on-duty ratio of the driving current is 10% or less; A circuit for a gas sensor module according to any one of claims 7 to 9.

11. The capacitor is a multilayer ceramic capacitor. A circuit for a gas sensor module according to any one of claims 7 to 10.

12. The capacitor has a capacitance of 1 mF or less. A circuit for a gas sensor module according to any one of claims 7 to 11.

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