Double-OSC constant temperature proportional control method and airflow detection chip

Abstract

The invention belongs to the technical field of integrated circuits, and provides a double-OSC constant-temperature proportional control method and an airflow detection chip, and the method comprises the steps: setting the basic frameworks of a first OSC and a second OSC to be consistent in advance, and after the capacitor frameworks of the first OSC and the second OSC are set in a differentiated manner, if the chip is powered on and does not receive an airflow input signal, starting the first OSC and the second OSC; if so, determining an initial frequency ratio of the second OSC to the first OSC; if the airflow input signal is received, determining a real-time frequency ratio of the second OSC to the first OSC; and determining a frequency ratio deviation value between the real-time frequency ratio and the initial frequency ratio, determining a deviation threshold value, and when the frequency ratio deviation value exceeds the deviation threshold value, triggering to output a working signal under the constant temperature ratio. According to the scheme, the precision of airflow detection is improved, and the triggering condition of the chip for outputting the working signal is stable because the frequency proportion of the double OSCs is not influenced by the temperature, so that the stability and the reliability of the output of the chip in various temperature environments are ensured.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to a dual OSC constant temperature proportional control method and an airflow detection chip. Background Technology

[0002] In the field of airflow detection, airflow detection chips built using OSCs (Oscillators) are widely used. These chips typically employ multiple OSCs, detecting airflow through the frequency ratio between them. Among them, airflow detection chips with a dual OSC structure have received considerable attention and application due to their relatively simple design and certain detection accuracy.

[0003] However, existing dual-OSC airflow detection chips suffer from significant temperature susceptibility. Because the oscillators lack consideration for temperature consistency, the internal component parameters of different oscillators change inconsistently with temperature variations, resulting in varying degrees of temperature-induced frequency interference. Consequently, the frequencies of the two OSCs shift to different degrees under varying temperature environments, causing changes in the frequency ratio between the two OSCs.

[0004] Due to the aforementioned issues, the airflow required for stable chip output fluctuates with temperature changes. This severely affects the detection accuracy and stability of the airflow detection chip, making it unable to accurately and reliably detect airflow in temperature-sensitive applications, thus greatly limiting the chip's application range and effectiveness.

[0005] Therefore, there is an urgent need for a method that can effectively reduce the influence of temperature on the frequency ratio of dual OSCs, achieve constant temperature ratio control, and thus improve the detection accuracy and stability of airflow detection chips. Summary of the Invention

[0006] This invention provides a dual-OSC constant temperature proportional control method and an airflow detection chip to solve the defects of traditional dual-OSC airflow detection chips, which are severely affected by temperature in the dual-OSC frequency ratio, resulting in low airflow detection accuracy and poor stability.

[0007] On one hand, the present invention provides a dual OSC constant temperature proportional control method, applied to an airflow detection chip comprising a first OSC and a second OSC, the method comprising:

[0008] After setting the basic architecture of the first OSC and the second OSC to be the same in advance and setting the capacitor architecture of the first OSC and the second OSC differently, if the chip is powered on and no airflow input signal is received, the initial frequency ratio of the second OSC to the first OSC is determined.

[0009] If an airflow input signal is received, the real-time frequency ratio between the second OSC and the first OSC is determined;

[0010] The frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio is determined, and a deviation threshold is determined. When the frequency ratio deviation exceeds the deviation threshold, a constant temperature proportional output signal is triggered.

[0011] According to the dual OSC constant temperature proportional control method provided by the present invention, the basic architecture of the first OSC and the second OSC is set to be consistent, including:

[0012] The relaxation oscillator structure is used as the framework structure for the first OSC and the second OSC.

[0013] The structures of the comparators within the framework of the first OSC and the second OSC are set to be completely identical.

[0014] The reference voltage and operating current of the first OSC and the second OSC are set to be the same.

[0015] According to the dual OSC constant temperature proportional control method provided by the present invention, the capacitor architecture of the first OSC and the second OSC are set differently, including:

[0016] Based on the capacitance of the gas sensor connected to the first OSC, a target capacitance value is determined, and a first capacitance value that satisfies the target capacitance value is set.

[0017] Determine the parasitic capacitance of the ESD protection circuit connected to the first OSC;

[0018] The first capacitor, the parasitic capacitor, and the capacitor of the gas sensor are used as the capacitor architecture of the first OSC.

[0019] Set a second capacitor and an auxiliary capacitor with opposite temperature coefficients;

[0020] The capacitance ratios of the second capacitor and the auxiliary capacitor are adjusted so that the temperature shifts of the second capacitor and the auxiliary capacitor cancel each other out.

[0021] The second capacitor and auxiliary capacitor, after adjusting their capacitance ratios, are used as the capacitor architecture for the second OSC.

[0022] According to the dual OSC constant temperature proportional control method provided by the present invention, the first capacitor is an adjustable capacitor, which includes a base fixed capacitor and multiple sub-capacitors; the method further includes:

[0023] Receive adjustment instructions during the chip manufacturing stage;

[0024] According to the adjustment instruction, an adjustment signal is sent to the adjustable capacitor so that the adjustable capacitor connects at least a portion of its sub-capacitors in parallel to the base fixed capacitor according to the adjustment signal.

[0025] According to the dual OSC constant temperature proportional control method provided by the present invention, the target capacitance value of the first capacitor is one-tenth to one-sixth of the capacitance of the gas sensor.

[0026] According to the dual OSC constant temperature proportional control method provided by the present invention, determining the deviation threshold value includes:

[0027] The deviation threshold value is calculated by quotienting the frequency ratio deviation with the initial frequency.

[0028] On the other hand, the present invention also provides an airflow detection chip, comprising: a first OSC, a second OSC, and a signal processing circuit;

[0029] Both the first OSC and the second OSC are connected to the signal processing circuit. The basic architecture of the first OSC and the second OSC is the same, but the capacitor architecture of the first OSC and the second OSC is set differently.

[0030] The signal processing circuit is used to determine the initial frequency ratio between the second OSC and the first OSC when the chip is powered on and no airflow input signal is received; to determine the real-time frequency ratio between the second OSC and the first OSC when an airflow input signal is received; to determine the frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio, and to determine a deviation threshold value; and to trigger the output working signal under constant temperature ratio when the frequency ratio deviation exceeds the deviation threshold value.

[0031] According to the airflow detection chip provided by the present invention, the frame structure of both the first OSC and the second OSC adopts a relaxation oscillator structure, the comparator structure within the frame structure of the first OSC and the second OSC is completely identical, and the reference voltage and operating current of the OSC and the second OSC are identical.

[0032] The airflow detection chip provided by the present invention further includes an ESD protection circuit.

[0033] The first OSC includes: a first capacitor and a first oscillation circuit;

[0034] The input terminal of the first OSC is connected to the ESD protection circuit, and the first capacitor and the ESD protection circuit are both connected to the first oscillation circuit.

[0035] The target capacitance value of the first capacitor is determined based on the capacitance of the gas sensor connected to the first OSC. The capacitor architecture of the first OSC includes the first capacitor, the parasitic capacitance of the ESD protection circuit, and the capacitance of the gas sensor.

[0036] According to the airflow detection chip provided by the present invention, the second OSC includes: a first MOSFET, a second capacitor, and a second oscillation circuit, wherein the first MOSFET and the second capacitor are both connected to the second oscillation circuit;

[0037] In this configuration, the auxiliary capacitor of the first MOSFET has the opposite temperature coefficient to the second capacitor. The capacitance ratios of the second capacitor and the auxiliary capacitor are pre-adjusted to cancel each other out in temperature shifts. The capacitor architecture of the second OSC includes the auxiliary capacitor of the first MOSFET and the second capacitor.

[0038] The dual OSC constant temperature proportional control method and airflow detection chip provided by this invention pre-set the basic architecture of the first OSC and the second OSC to be the same, and differentiate the capacitor architecture of the first OSC and the second OSC; when powered on and no airflow input signal is received, the initial frequency ratio of the second OSC and the first OSC is determined; when an airflow input signal is received, the real-time frequency ratio of the second OSC and the first OSC is determined; the frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio is determined, and a deviation threshold value is determined; when the frequency ratio deviation exceeds the deviation threshold value, the constant temperature proportional output working signal is triggered. This solution ensures consistency in temperature coefficients by setting the basic architecture of the first and second OSCs to be identical. By differentiating the capacitor architecture, the capacitor of the second OSC can also have characteristics such as zero temperature coefficient. This allows the frequency ratio of the two OSCs to remain basically constant when the temperature changes. Based on the frequency ratio detection method, the frequency changes of the first OSC caused by airflow can be accurately captured, improving the accuracy of airflow detection. Since the frequency ratio of the two OSCs is not affected by temperature, the triggering conditions of the chip's output working signal are stable, ensuring the stability and reliability of the chip's output under various temperature environments. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a flowchart illustrating the dual OSC constant temperature proportional control method provided in an embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the implementation principle of the gas flow detection stage in this embodiment of the invention;

[0042] Figure 3 This is a schematic diagram of the circuit structure of the first OSC and the second OSC in an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the internal circuit structure of the adjustable capacitor in an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the airflow detection chip provided in an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] The following is combined with Figures 1 to 5 This invention describes the detailed scheme of the dual OSC constant temperature proportional control method and the airflow detection chip provided in the embodiments of the present invention.

[0047] like Figure 1 As shown, the dual OSC constant temperature proportional control method provided in this embodiment of the invention can be applied to an airflow detection chip that includes a first OSC and a second OSC. The method mainly includes the following steps:

[0048] Step 110: After setting the basic architecture of the first OSC and the second OSC to be the same and setting the capacitor architecture of the first OSC and the second OSC differently, if the chip is powered on and no airflow input signal is received, the initial frequency ratio of the second OSC to the first OSC is determined.

[0049] Understandably, to avoid differences in temperature coefficients between the first and second OSCs due to hardware variations, which could affect the frequency ratio, this embodiment first unifies the basic architecture of the first and second OSCs. Furthermore, since the OSC frequency is determined by its operating current and capacitance, the capacitor design needs to be optimized separately for the different functional roles of the first and second OSCs.

[0050] In this embodiment, when the airflow detection chip is powered on and there is no airflow input, the initial frequency ratio of the second OSC to the first OSC can be automatically recorded. At this time, the airflow detection chip has no output and no heat generation.

[0051] Step 120: If an airflow input signal is received, determine the real-time frequency ratio between the second OSC and the first OSC.

[0052] When airflow is input to the airflow detection chip, the capacitance of the gas sensor changes, causing the frequency of the first OSC to change, which in turn causes the real-time frequency ratio to change.

[0053] Step 130: Determine the frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio, and determine the deviation threshold. When the frequency ratio deviation exceeds the deviation threshold, trigger the output working signal under constant temperature proportional.

[0054] In this embodiment, when the frequency ratio deviation exceeds the deviation threshold, the airflow detection chip triggers a stable output. Since the frequency ratio of the dual OSCs has been eliminated by the hardware design to eliminate the influence of temperature, the deviation threshold does not change with temperature. Therefore, the gas flow rate required for the airflow detection chip to output stably is also fixed.

[0055] The implementation principle of the gas flow detection process is as follows: Figure 2 As shown, see Figure 2 The output terminal of the gas sensor 210 is connected to the input terminal SEN of the first OSC 220 in the airflow detection chip 200. Therefore, the SEN terminal can be configured with the ESD protection circuit 230.

[0056] When different gas flow rates pass through the gas sensor 210, the capacitance of the gas sensor 210 changes with the flow rate, and the frequency of the first OSC 220 changes accordingly. When there is no gas flow, the airflow detection chip 200 records the initial frequency ratio between the second OSC 240 and the first OSC 220 after power-on. When there is gas flow, if the deviation between the real-time frequency ratio of the second OSC 240 and the first OSC 220 and the initial frequency ratio exceeds the deviation threshold, the airflow detection chip 200 will operate stably, generating heat during operation.

[0057] In one embodiment, the infrastructure of the first OSC and the second OSC is set to be consistent, specifically including:

[0058] On the one hand, the relaxation oscillator structure is used as the framework structure for the first OSC and the second OSC.

[0059] On the other hand, the structures of the comparators within the framework of the first OSC and the second OSC are set to be completely identical.

[0060] On the other hand, the reference voltage and operating current of the first OSC and the second OSC are set to be the same.

[0061] In this embodiment, as Figure 3 As shown, both the first OSC 220 and the second OSC 240 adopt a relaxation oscillator structure, and their comparator structures are the same. They share a common reference voltage, and their operating currents satisfy ib1=ib2. Both operating currents are obtained by mirroring the current of the ibias circuit. Therefore, the temperature coefficients of the first OSC 220 and the second OSC 240 are consistent, which can eliminate the influence of temperature on the deviation threshold.

[0062] In one embodiment, the capacitor architecture of the first OSC and the second OSC are differentiated, specifically including:

[0063] On the one hand, based on the capacitance of the gas sensor connected to the first OSC, a target capacitance value is determined, and a first capacitance that satisfies the target capacitance value is set.

[0064] On the other hand, the parasitic capacitance of the ESD protection circuit in the first OSC is determined.

[0065] Finally, the first capacitor, the parasitic capacitor, and the gas sensor capacitor are used as the capacitor architecture of the first OSC.

[0066] At the same time, a second capacitor and an auxiliary capacitor with opposite temperature coefficients are set.

[0067] Then, the capacitance ratios of the second capacitor and the auxiliary capacitor are adjusted so that the temperature shifts of the second capacitor and the auxiliary capacitor cancel each other out.

[0068] Finally, the second capacitor and auxiliary capacitor with adjusted capacitance ratios are used as the capacitor architecture for the second OSC.

[0069] like Figure 2 As shown, the output frequencies of the first OSC and the second OSC are respectively:

[0070]

[0071] The capacitor architectures of the first OSC and the second OSC are as follows:

[0072] C_osc1=C1+C_ESD+C_gas sensor(3)

[0073] C_osc2=C2+C_MN3 (4)

[0074] Wherein, C_osc2 represents the oscillator terminal capacitance of the second OSC when there is no airflow, C_osc1 represents the oscillator terminal capacitance of the first OSC when there is no airflow, f_osc1 represents the output frequency of the first OSC when there is no airflow, f_osc2 represents the output frequency of the second OSC when there is no airflow, ib1 represents the operating current of the first OSC, ib2 represents the operating current of the second OSC, vref represents the reference voltage, C1 represents the first capacitor, C_ESD represents the parasitic capacitance of the ESD protection circuit, C_gas sensor represents the capacitance of the gas sensor, C2 represents the second capacitor, and C_MN3 represents the auxiliary capacitor.

[0075] Since ib1 = ib2, the real-time frequency ratio of the first OSC to the second OSC when there is airflow can be expressed as:

[0076]

[0077]

[0078] Where C_osc2' represents the oscillator terminal capacitance of the second OSC when there is airflow, C_osc1' represents the oscillator terminal capacitance of the first OSC when there is airflow, f_osc1' represents the output frequency of the first OSC when there is airflow, f_osc2' represents the output frequency of the second OSC when there is airflow, ΔC_osc1 represents the capacitance change of the first OSC caused by airflow, and ΔC_osc2 represents the capacitance change of the second OSC caused by airflow.

[0079] An airflow impact analysis of the first OSC yields the following results:

[0080]

[0081] Wherein, ΔC1 represents the capacitance change of the first capacitor caused by airflow, ΔC_ESD represents the capacitance change of the parasitic capacitance of the ESD protection circuit caused by airflow, and ΔC_gas_sensor represents the capacitance change of the gas sensor caused by airflow.

[0082] As can be seen from the above expression, once the deviation threshold is set, the smaller the first capacitor C1, the smaller the gas flow rate required for the gas flow detection chip to output stably. Therefore, in this embodiment, the capacitance value of the first capacitor C1 is set to one-tenth to one-sixth of the gas sensor capacitance. Because the capacitance value of the first capacitor C1 is relatively small, in practical applications, the first capacitor can be a capacitor with a small temperature coefficient, such as a trap capacitor.

[0083] In some embodiments, in order to reduce the temperature effect on the parasitic capacitance of the ESD protection circuit, the ESD protection circuit can use an ESD protection diode, which has a smaller temperature coefficient of parasitic capacitance.

[0084] Therefore, the analysis of the airflow impact on the first OSC can be expressed as:

[0085]

[0086] Meanwhile, an airflow impact analysis of the second OSC yields the following results:

[0087]

[0088] Where ΔC2 represents the change in capacitance of the second capacitor caused by airflow, and ΔC_MN3 represents the change in capacitance of the auxiliary capacitor caused by airflow.

[0089] Therefore, the second OSC uses two capacitor types with opposite temperature coefficients, such as well capacitors and MOS capacitors. By adjusting the capacitance ratio of the two, the zero temperature coefficient of the deviation threshold can be achieved while keeping the total capacitance constant.

[0090] In one embodiment, determining the deviation threshold specifically includes:

[0091] The deviation threshold value is calculated by quotienting the frequency ratio deviation with the initial frequency.

[0092] In this embodiment, the formula for calculating the deviation threshold is as follows:

[0093]

[0094] Where f_osc2 / f_osc1 represents the initial frequency ratio of the second OSC to the first OSC when there is no airflow, and f_osc2' / f_osc1' represents the real-time frequency ratio of the second OSC to the first OSC when there is airflow.

[0095] Based on the above reasoning, the real-time frequency ratio of the second OSC to the first OSC can be expressed as:

[0096]

[0097] Since the ΔC pneumatic sensor is only related to the gas flow rate, meaning the real-time frequency ratio of the second OSC to the first OSC is not affected by temperature, we can then obtain:

[0098]

[0099] ΔC_gas_sensor = Deviation threshold * (C1 + C_ESD + C_gas_sensor) (15)

[0100] Once the deviation threshold is fixed, the value of the ΔC gas sensor is fixed, and the gas flow rate required for the gas flow detection chip to output stably is fixed, thus it is not affected by temperature stability.

[0101] In one embodiment, the first capacitor is an adjustable capacitor, which includes a base fixed capacitor and multiple sub-capacitors; the method may further include:

[0102] First, it receives adjustment instructions from the chip manufacturing stage.

[0103] In practical applications, adjustment instructions can be manually triggered by relevant personnel after production is completed. For example, they can click the adjustment button on the human-machine interface, or they can actively input the relevant target parameters for adjustment to trigger the adjustment process.

[0104] Then, according to the adjustment instruction, an adjustment signal is sent to the adjustable capacitor, so that the adjustable capacitor connects at least a portion of its sub-capacitors in parallel to the base fixed capacitor according to the adjustment signal.

[0105] In this embodiment, considering the influence of actual production process angle, the first capacitor C1 in the first OSC can be an adjustable capacitor. In practical applications, by trim programming, the gas flow rate of all gas flow detection chips can be made consistent when outputting stably.

[0106] Figure 4 The internal structure of the adjustable capacitor is shown, such as... Figure 4 As shown, C0 is the base fixed capacitor and the core component of the adjustable capacitor, providing the initial capacitance value. C3, C4, and C5 are all configurable sub-capacitors, and the total capacitance value can be adjusted through different on / off combinations. MN4, MN5, and MN6 are three MOSFETs, acting as switching elements, whose on / off state is controlled by the trim signal. <0> Trim <1> Trim <2> To adjust the signal, it is necessary to determine whether the three MOSFETs are turned on, thereby selecting the sub-capacitors to be connected to the circuit.

[0107] Specifically, by controlling the high and low levels of the adjustment signal, the three MOS transistors can be turned on or off, thereby selectively connecting the three sub-capacitors in parallel to the base fixed capacitor C0, thus adjusting the total capacitance value. Through this adjustment method, the total capacitance value of the adjustable capacitors can be adjusted before the airflow detection chip leaves the factory to compensate for process deviations and ensure that the adjustable capacitance of all airflow detection chips approaches the design target value, thereby ensuring that the gas flow rate is consistent when all airflow detection chips output stably.

[0108] Based on the same general inventive concept, this invention also protects an airflow detection chip. The airflow detection chip provided by this invention will be described below. The airflow detection chip described below and the dual OSC constant temperature proportional control method described above can be referred to in correspondence.

[0109] like Figure 5As shown, the airflow detection chip provided in this embodiment of the invention specifically includes: a first OSC 220, a second OSC 240, and a signal processing circuit 250.

[0110] Both the first OSC 220 and the second OSC 240 are connected to the signal processing circuit 250. The basic architecture of the first OSC 220 and the second OSC 240 is the same, but the capacitor architecture of the first OSC 220 and the second OSC 240 is set differently.

[0111] The signal processing circuit 250 is used to determine the initial frequency ratio between the second OSC 240 and the first OSC 220 when the circuit is powered on and no airflow input signal is received; to determine the real-time frequency ratio between the second OSC 240 and the first OSC 220 when an airflow input signal is received; to determine the frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio, and to determine the deviation threshold value; and to trigger the output working signal under constant temperature proportional mode when the frequency ratio deviation exceeds the deviation threshold value.

[0112] In one embodiment, the frame structure of both the first OSC and the second OSC adopts a relaxation oscillator structure, the comparator structure within the frame structure of the first OSC and the second OSC is completely identical, and the reference voltage and operating current of the OSC and the second OSC are identical.

[0113] like Figure 2 and Figure 5 As shown, the airflow detection chip also includes an ESD protection circuit 230.

[0114] The first OSC 220 includes: a first capacitor C1 and a first oscillation circuit 221.

[0115] The input terminal of the first OSC 220 is connected to the ESD protection circuit 230, and both the ESD protection circuit 230 and the first capacitor C1 are connected to the first oscillation circuit 221.

[0116] The target capacitance value of the first capacitor C1 is determined based on the capacitance of the gas sensor 210 connected to the first OSC 220. The capacitor architecture of the first OSC 220 includes the first capacitor C1, the parasitic capacitance of the ESD protection circuit 230, and the capacitance of the gas sensor 210.

[0117] In one embodiment, such as Figure 2 and Figure 5 As shown, the second OSC 240 includes: a first MOS transistor MN3, a second capacitor C2, and a second oscillation circuit 241. The first MOS transistor MN3 and the second capacitor C2 are both connected to the second oscillation circuit 241.

[0118] In this design, the auxiliary capacitor of the first MOSFET MN3 has the opposite temperature coefficient to the second capacitor C2. The capacitance ratios of the second capacitor C2 and the auxiliary capacitor are pre-adjusted so that the temperature shifts of the second capacitor C2 and the auxiliary capacitor cancel each other out. The capacitor architecture of the second OSC240 includes the auxiliary capacitor of the first MOSFET MN3 and the second capacitor C2.

[0119] like Figure 2 As shown, the first oscillation circuit 221 includes: a second MOS transistor MN1, a first comparator CMP1, a first inverter INV1, and a first buffer 1. The second MOS transistor MN1 is connected to the first input terminal of the first comparator CMP1, and the output terminal of the first comparator CMP1, the first inverter INV1, and the first buffer 1 are connected in sequence.

[0120] like Figure 2 As shown, the second oscillation circuit 241 includes: a third MOS transistor MN2, a second comparator CMP2, a second inverter INV2, and a second buffer 2. The second MOS transistor MN2 is connected to the second input terminal of the second comparator CMP2, the first input terminal of the second comparator CMP2 is connected to the second input terminal of the first comparator CMP1, and the output terminal of the second comparator CMP2, the second inverter INV2, and the second buffer 2 are connected in sequence.

[0121] In summary, this embodiment ensures the consistency of the temperature coefficients of the two OSCs and the temperature stability of the second OSC capacitor by setting the basic architecture of the first OSC and the second OSC to be consistent, while differentiating the capacitor architecture. This makes the frequency ratio between the two OSCs unaffected by temperature. The initial frequency ratio is determined when there is no airflow, and the real-time frequency ratio is determined when there is airflow. The output is triggered by comparing the frequency ratio deviation with the deviation threshold, which can accurately capture the frequency changes of the first OSC caused by airflow and significantly improve the detection accuracy. Moreover, because the frequency ratio of the two OSCs is stable, the output triggering condition of the pneumatic detection chip is not affected by temperature fluctuations, ensuring the stability and reliability of the output. This can meet the needs of multiple scenarios such as precision industrial gas detection and high-precision environmental monitoring.

[0122] Regarding the pneumatic detection chip in the above embodiments, the specific working relationship of each structure has been described in detail in the embodiments of the relevant methods, and will not be elaborated further here.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual OSC constant temperature proportional control method, characterized in that, The method, applied to an airflow detection chip comprising a first OSC and a second OSC, includes: After setting the basic architecture of the first OSC and the second OSC to be the same in advance and setting the capacitor architecture of the first OSC and the second OSC differently, if the chip is powered on and no airflow input signal is received, the initial frequency ratio of the second OSC to the first OSC is determined. If an airflow input signal is received, the real-time frequency ratio between the second OSC and the first OSC is determined; The frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio is determined, and a deviation threshold is determined. When the frequency ratio deviation exceeds the deviation threshold, a constant temperature proportional output signal is triggered.

2. The dual OSC constant temperature proportional control method according to claim 1, characterized in that, Set the infrastructure of the first OSC and the second OSC to be consistent, including: The relaxation oscillator structure is used as the framework structure for the first OSC and the second OSC. The structures of the comparators within the framework of the first OSC and the second OSC are set to be completely identical. The reference voltage and operating current of the first OSC and the second OSC are set to be the same.

3. The dual OSC constant temperature proportional control method according to claim 1, characterized in that, Differentiated settings for the capacitor architecture of the first OSC and the second OSC include: Based on the capacitance of the gas sensor connected to the first OSC, a target capacitance value is determined, and a first capacitance value that satisfies the target capacitance value is set. Determine the parasitic capacitance of the ESD protection circuit connected to the first OSC; The first capacitor, the parasitic capacitor, and the capacitor of the gas sensor are used as the capacitor architecture of the first OSC. Set a second capacitor and an auxiliary capacitor with opposite temperature coefficients; The capacitance ratios of the second capacitor and the auxiliary capacitor are adjusted so that the temperature shifts of the second capacitor and the auxiliary capacitor cancel each other out. The second capacitor and auxiliary capacitor, after adjusting their capacitance ratios, are used as the capacitor architecture for the second OSC.

4. The dual OSC constant temperature proportional control method according to claim 3, characterized in that, The first capacitor is an adjustable capacitor, which includes a base fixed capacitor and multiple sub-capacitors; the method further includes: Receive adjustment instructions during the chip manufacturing stage; According to the adjustment instruction, an adjustment signal is sent to the adjustable capacitor so that the adjustable capacitor connects at least a portion of its sub-capacitors in parallel to the base fixed capacitor according to the adjustment signal.

5. The dual OSC constant temperature proportional control method according to claim 3 or 4, characterized in that, The target capacitance value of the first capacitor is one-tenth to one-sixth of the capacitance of the gas sensor.

6. The dual OSC constant temperature proportional control method according to claim 1, characterized in that, Determine the deviation threshold, including: The deviation threshold value is calculated by quotienting the frequency ratio deviation with the initial frequency.

7. An airflow detection chip, characterized in that, include: First OSC, second OSC, and signal processing circuitry; Both the first OSC and the second OSC are connected to the signal processing circuit. The basic architecture of the first OSC and the second OSC is the same, but the capacitor architecture of the first OSC and the second OSC is set differently. The signal processing circuit is used to determine the initial frequency ratio of the second OSC to the first OSC when the chip is powered on and no airflow input signal is received; Upon receiving an airflow input signal, the real-time frequency ratio between the second OSC and the first OSC is determined; the frequency ratio deviation between the real-time frequency ratio and the initial frequency ratio is determined, and a deviation threshold is determined; when the frequency ratio deviation exceeds the deviation threshold, a constant temperature proportional output working signal is triggered.

8. The airflow detection chip according to claim 7, characterized in that, Both the first OSC and the second OSC adopt a relaxation oscillator structure in their frame structure. The comparator structures within the frame structures of the first OSC and the second OSC are completely identical. The reference voltage and operating current of the OSC and the second OSC are also identical.

9. The airflow detection chip according to claim 7, characterized in that, The airflow detection chip also includes an ESD protection circuit. The first OSC includes: a first capacitor and a first oscillation circuit; The input terminal of the first OSC is connected to the ESD protection circuit, and the first capacitor and the ESD protection circuit are both connected to the first oscillation circuit. The target capacitance value of the first capacitor is determined based on the capacitance of the gas sensor connected to the first OSC. The capacitor architecture of the first OSC includes the first capacitor, the parasitic capacitance of the ESD protection circuit, and the capacitance of the gas sensor.

10. The airflow detection chip according to claim 7, characterized in that, The second OSC includes: a first MOSFET, a second capacitor, and a second oscillation circuit, wherein the first MOSFET and the second capacitor are both connected to the second oscillation circuit; In this configuration, the auxiliary capacitor of the first MOSFET has the opposite temperature coefficient to the second capacitor. The capacitance ratios of the second capacitor and the auxiliary capacitor are pre-adjusted to cancel each other out in temperature shifts. The capacitor architecture of the second OSC includes the auxiliary capacitor of the first MOSFET and the second capacitor.

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