Blood oxygen measurement circuit, measurement device and measurement method

Abstract

The present invention relates to the field of medical equipment technology, and more specifically to a blood oxygen measurement circuit, a measurement device, and a measurement method. The measurement circuit includes a receiving circuit; a driving circuit having a transistor unit and an internal resistance adjustment unit, the internal resistance adjustment unit being connected to the transistor unit; and a processing circuit connected to the receiving circuit and the internal resistance adjustment unit, respectively. The processing circuit is configured to adjust the internal resistance adjustment unit based on the magnitude of a driving current of the driving circuit to adjust the internal resistance of transistors in the transistor unit, and to determine blood oxygen levels based on a received signal from the receiving circuit. The internal resistance of the transistors in the transistor unit is adjusted so that the internal resistance of the transistors changes with the magnitude of the driving current, thereby causing the transistors to operate in a region with a minimal internal resistance change rate within the entire driving current range, thereby reducing noise in the entire blood oxygen measurement circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of medical equipment, and in particular to a blood oxygen measurement circuit, a measurement device, and a measurement method. Background Art

[0002] Pulse oximetry is commonly used to monitor a patient's blood oxygen level due to its non-invasive, simple, and continuous monitoring capabilities. This technology utilizes pulse oximetry to measure the percentage of oxygenated hemoglobin relative to total hemoglobin by detecting changes in light absorption by arterial blood. The specific measurement principle involves placing a sensor on a test site, such as a finger, forehead, earlobe, or toe, and illuminating the skin surface perpendicularly with two different wavelengths of light. The intensity of the transmitted or reflected light is absorbed by the blood and tissues, varying with the pulse, and blood oxygen is calculated.

[0003] In the measurement principle, the circuit used to drive the two light sources is called the driver circuit, and the circuit used to receive the transmitted light is called the receiver circuit. These two circuits constitute the core of the blood oxygen measurement circuit. The driver circuit generally uses a constant current drive method, that is, the light-emitting diode is controlled by a variable constant current.

[0004] The operating principle of a commonly used blood oximetry circuit in the prior art is that a drive current control circuit outputs an analog voltage to a signal conditioning circuit, which then controls the transistor's on-resistance. Since the transistor's on-resistance varies with different drive currents, adjusting the transistor's on-resistance allows for different drive currents for the light-emitting unit. To achieve constant current drive, the transistor must operate in a variable resistance region. When the drive current is relatively low, meaning the control signal from the drive current control circuit is relatively small, the transistor's on-resistance is relatively high, while other circuit parameters remain unchanged. At this point, the transistor operates in a region with a high rate of change in internal resistance. Therefore, even a slight change in the drive current control circuit can cause a significant change in the transistor's on-resistance. This results in significant variations in the circuit's drive current at a given drive current, which manifests as high noise in the blood oximetry circuit. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a blood oxygen measurement circuit, a measurement device, and a measurement method to solve the problem of high noise in the blood oxygen measurement circuit.

[0006] According to a first aspect, an embodiment of the present invention provides a blood oxygen measurement circuit, including:

[0007] receiving circuit;

[0008] A driving circuit comprising a transistor unit and an internal resistance adjustment unit, wherein the internal resistance adjustment unit is connected to the transistor unit;

[0009] A processing circuit is connected to the receiving circuit and the internal resistance adjustment unit, respectively. The processing circuit is used to adjust the internal resistance adjustment unit based on the size of the driving current of the driving circuit to adjust the internal resistance of the transistor in the transistor unit, and determine the blood oxygen based on the received signal of the receiving circuit.

[0010] The blood oxygen measurement circuit provided in an embodiment of the present invention provides an internal resistance adjustment unit in the driving circuit. The internal resistance adjustment unit is adjusted by a processing circuit based on the magnitude of the driving current of the driving circuit. That is, the internal resistance of the transistor in the transistor unit is adjusted so that the internal resistance of the transistor changes with the magnitude of the driving current. This allows the transistor to operate in a region with a small internal resistance change rate as much as possible within the entire driving current range, thereby reducing the noise of the blood oxygen driving circuit and, in turn, the noise of the entire blood oxygen measurement circuit.

[0011] In combination with the first aspect, in a first embodiment of the first aspect, the first end of the transistor is grounded through the internal resistance adjustment unit, and the processing circuit is used to adjust the resistance value of the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit.

[0012] In the blood oxygen measurement circuit provided in an embodiment of the present invention, an internal resistance adjustment unit is connected to the first end of the transistor and serves as the current-limiting resistor of the transistor. The processing circuit can adjust the resistance value of the internal resistance adjustment unit so that the transistor operates in a region with a small internal resistance change rate. The internal resistance of the transistor is adjusted by changing the resistance value of the current-limiting resistor. The circuit structure is simple, easy to implement, and low in cost.

[0013] In combination with the first embodiment of the first aspect, in the second embodiment of the first aspect, the internal resistance adjustment unit includes:

[0014] a resistance unit connected to the first end of the transistor;

[0015] A switch circuit unit is connected to the resistance unit and the processing circuit respectively, and the switch circuit is used to adjust the resistance value of the resistance unit based on a control signal sent by the processing circuit.

[0016] The blood oxygen measurement circuit provided by the embodiment of the present invention uses a switch circuit unit to adjust the resistance value of the resistance unit, has a simple structure, and reduces the circuit volume.

[0017] In combination with the second embodiment of the first aspect, in the third embodiment of the first aspect, the resistance unit includes at least two resistors, and the switching circuit unit is connected in series or in parallel with at least one of the resistors.

[0018] In combination with the third embodiment of the first aspect, in the fourth embodiment of the first aspect, the switch circuit unit is a selection switch unit, and each selection branch of the selection switch unit is respectively connected to the resistor in the resistance unit.

[0019] In combination with the third embodiment of the first aspect, in the fifth embodiment of the first aspect, the at least two resistors are connected in parallel, the switch circuit unit includes at least one switch, and the switch is connected in series with the resistors;

[0020] or,

[0021] The at least two resistors are connected in series, and the switch circuit unit includes at least one switch, which is connected in parallel with the resistors.

[0022] In combination with the first embodiment of the first aspect, in the fifth embodiment of the first aspect, the internal resistance adjustment unit includes a digital potentiometer, and the digital potentiometer is respectively connected to the first end of the transistor and the processing circuit.

[0023] The blood oxygen measurement circuit provided in the embodiment of the present invention uses a digital potentiometer to adjust the resistance value, which saves the use of switch circuit units, further simplifies the circuit structure, and reduces the circuit volume.

[0024] In combination with the first aspect, in a seventh implementation of the first aspect, the blood oxygen measurement circuit further includes:

[0025] A light-emitting circuit having a light-emitting diode;

[0026] The internal resistance adjustment unit is a variable voltage driving source, which is connected to the light emitting circuit and is used to drive the light emitting tube to emit light.

[0027] In combination with the first aspect, or any one of the first to seventh embodiments of the first aspect, in a sixth embodiment of the first aspect, the transistor unit further includes:

[0028] a driving current control circuit connected to the processing circuit, the processing circuit being further configured to determine the magnitude of the driving current based on a received signal from the receiving circuit, and to control the driving current control circuit to output a corresponding analog voltage signal;

[0029] A signal conditioning circuit, wherein the input end is connected to the output end of the driving current control circuit, the output end of the signal conditioning circuit is connected to the second end of the transistor, and the signal conditioning circuit is used to process the analog voltage signal and then output it to the transistor.

[0030] In the blood oxygen measurement circuit provided by the embodiment of the present invention, the processing circuit controls the magnitude of the driving current using the received signal, so that the driving current can meet the measurement requirements, thereby improving the measurement accuracy.

[0031] According to a second aspect, an embodiment of the present invention further provides a blood oxygen measurement device, including:

[0032] Equipment body;

[0033] The blood oxygen measurement circuit described in the first aspect of the present invention, or any embodiment of the first aspect, is arranged in the device body.

[0034] The blood oxygen measurement device provided in an embodiment of the present invention provides an internal resistance adjustment unit in the driving circuit. The internal resistance adjustment unit is adjusted by a processing circuit based on the magnitude of the driving current of the driving circuit. That is, the internal resistance of the transistor in the transistor unit is adjusted so that the internal resistance of the transistor changes with the magnitude of the driving current. This allows the transistor to operate in a region with a small internal resistance change rate as much as possible within the entire driving current range, thereby reducing the noise of the blood oxygen driving circuit and, in turn, the noise of the blood oxygen measurement device.

[0035] According to a third aspect, an embodiment of the present invention provides a blood oxygen measurement method, which is applied to the processing circuit of the blood oxygen measurement circuit according to the first aspect of the present invention, or any embodiment of the first aspect, and includes:

[0036] Obtaining the magnitude of the driving current of the driving circuit;

[0037] adjusting the internal resistance adjusting unit based on the magnitude of the driving current of the driving circuit to adjust the internal resistance of the transistor in the transistor unit;

[0038] Acquire a first received signal from the receiving circuit;

[0039] Blood oxygen is determined based on the first received signal.

[0040] The blood oxygen measurement method provided by an embodiment of the present invention adjusts the internal resistance of the transistor in the transistor unit so that the internal resistance of the transistor changes with the magnitude of the driving current. This allows the transistor to operate as close to the region of internal resistance change rate as possible within the entire driving current range, thereby reducing the noise of the blood oxygen drive circuit and, in turn, the noise of the entire blood oxygen measurement circuit, thereby improving the accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 Shows a structural block diagram of the blood oxygen measurement circuit;

[0043] Figure 2 is a schematic diagram of a measurement principle according to an embodiment of the present invention;

[0044] Figure 3 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0045] Figure 4 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0046] Figure 5 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0047] Figure 6 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0048] Figure 7 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0049] Figure 8 is a structural block diagram of a blood oxygen measurement circuit according to an embodiment of the present invention;

[0050] Figure 9 FIG. 4 is a flow chart of a blood oxygen measurement method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0052] Figure 1This diagram shows an optional structural diagram of a blood oxygen measurement circuit. The measurement circuit includes a receiving circuit, a driving circuit, and a processing circuit. The operating principle of this measurement circuit is as follows: the processing circuit 112 controls the driving circuit to cause the light-emitting diode to emit light according to a preset driving current. The receiving diode converts the light signal into a current signal. The receiving circuit then converts the analog signal into a digital signal, which is then sent to the processing circuit 112 for processing. The processing circuit 112 calculates the blood oxygen level based on the received digital signal. The driving circuit generally uses a constant current drive method, meaning that the light-emitting diode is controlled by a variable constant current.

[0053] However, in the above-mentioned measurement circuit, in order to achieve the purpose of constant current control, when the driving current is small and other circuit parameters remain unchanged, the transistor operates in a region with a large internal resistance change rate. At this time, a slight change in the driving current control circuit will cause a large change in the transistor's on-state internal resistance, which in turn causes the measurement circuit to have a large noise.

[0054] To clearly describe the principle of the blood oxygen measurement circuit described in the embodiment of the present invention, the relationship between the driving voltage VGS and the on-state internal resistance RDS of the transistor is expressed as follows:

[0055] Figure 2 shows the transistor drive power supply V GS and the on-resistance R DS relationship, specifically, combined Figure 1 In the driving circuit shown, the smaller the driving voltage, the greater the rate of change of the on-state internal resistance; the larger the driving voltage, the smaller the rate of change of the on-state internal resistance, and the two are similar to an exponential function relationship. When the driving voltage is small, such as Figure 2 In the AB section shown, even a small noise on the driving voltage will cause a large change in the on-resistance, which in turn causes a large change in the driving current. This is manifested as a large driving current noise at a certain driving voltage, which in turn causes a large noise in the entire measurement circuit. If the transistor is operated in a range with a small on-resistance change rate, such as Figure 2 In the BC segment shown, even if there is a small noise in the driving voltage, the driving current noise will also be small due to the small change rate of the transistor's on-resistance. This achieves a simpler solution and significantly reduces the noise of the entire measurement circuit.

[0056] Based on this, an embodiment of the present invention provides a blood oxygen measurement circuit. This measurement circuit is improved by providing an internal resistance adjustment unit, which enables the transistor to operate in a region with a low internal resistance change rate throughout the entire drive current range. The region with a low internal resistance change rate is specifically determined based on the actual application scenario of the measurement circuit and is not limited to a specific range. Furthermore, by enabling the transistor to operate in a region with a low internal resistance change rate, the purpose is to reduce noise in the measurement circuit.

[0057] For the convenience of the following description, Figure 4 , the driving current and driving signal involved below are explained as follows:

[0058] Driving current: the current in the driving circuit, that is, the current flowing through the light-emitting tube 101, the light source driving power supply 102, the analog switch circuit 103, the transistor 104 and the internal resistance adjustment unit;

[0059] Driving signal: the signal output by the processing circuit 112 to the driving current control circuit 107 .

[0060] The embodiment of the present invention provides a blood oxygen measurement circuit, such as Figure 3 As shown, the measurement circuit includes a receiving circuit 1, a driving circuit 2, and a processing circuit 112. The overall operating principle of the measurement circuit is as follows: the processing circuit 112 controls the driving circuit 2, causing the light-emitting diode in the driving circuit 2 to emit light according to the set driving current. The receiving diode in the receiving circuit 1 converts the light signal into a current signal. After processing by the receiving circuit 1, the analog signal is converted into a digital signal and sent to the processing circuit 112 for processing to calculate the blood oxygen level.

[0061] Specifically, the driving circuit 2 includes a transistor unit and an internal resistance adjustment unit, which is connected to the transistor unit. Under the control of the processing circuit 112, the internal resistance adjustment unit is used to adjust the internal resistance of the transistors in the transistor unit, so that the transistors operate in a region with a small internal resistance change rate under different driving currents.

[0062] The internal resistance adjustment unit can be connected to the first end of the transistor and used as the current limiting resistor of the transistor. That is, the internal resistance of the transistor is adjusted by adjusting the resistance value of the current limiting resistor of the transistor. For example, the resistance value can be adjusted by cooperating with the resistor and the switch, etc. The specific principle is: the transistor 104 and the internal resistance adjustment unit are regarded as an adjustable whole. If constant current source control is to be achieved, the voltage across the adjustable whole must be kept constant while other circuit parameters remain unchanged. When the driving current decreases, the resistance value of the adjustable whole increases. Accordingly, the resistance value of the internal resistance adjustment unit is adjusted so that its output resistance value increases; when the driving current increases, the resistance value of the adjustable whole decreases. Accordingly, the resistance value of the internal resistance adjustment unit is adjusted so that its output resistance value decreases.

[0063] The internal resistance adjustment unit can also be Figure 1The analog switch circuit 103 shown is connected, that is, it is used as a light source driving power supply, and the internal resistance of the transistor is adjusted by adjusting the size of the light source driving power supply. For example, the size of the light source driving power supply can be adjusted by coordinating light source driving power supplies of different voltage levels with switches, and so on. This setting has corresponding prerequisites, that is, when the transistor 104 is completely turned on, the total voltage of the light-emitting tube, the light source driving power supply, the analog switch circuit, the transistor and the current limiting resistor cannot exceed the voltage of the light source driving power supply. The adjustment principle is: if you want to achieve constant current source control, when other circuit parameters remain unchanged, it is necessary to ensure that the voltage at both ends of the adjustable whole is constant. When the driving current decreases, the adjustable whole voltage becomes smaller, and the internal resistance of the transistor is adjusted by reducing the output voltage of the light source driving power supply.

[0064] Of course, the internal resistance adjustment unit can also be set at other positions of the driving circuit. There is no limitation on its specific setting position and structure. It can be set accordingly according to actual conditions.

[0065] like Figure 3 As shown, the processing circuit 112 is connected to the receiving circuit 1 and the internal resistance adjustment unit. The processing circuit 112 is used to adjust the internal resistance adjustment unit based on the driving current of the driving circuit, for example, adjusting the resistance value of the internal resistance adjustment unit, or adjusting the output power of the internal resistance adjustment unit. By adjusting the internal resistance adjustment unit, the internal resistance of the transistors in the transistor unit is adjusted, thereby ensuring that the transistors operate in a region with a small internal resistance change rate under different driving currents.

[0066] Specifically, the processing circuit 112 determines the adjustment of the internal resistance adjustment unit based on the current driving current. When the internal resistance adjustment unit is used to adjust the resistance of the current limiting resistor of the transistor, the processing circuit 112 can determine the resistance of the current limiting resistor required based on the current driving current, and then form a control instruction to adjust the resistance of the internal resistance adjustment unit. For example, the processing circuit 112 can be implemented by multiple comparison circuits and logic circuits. The multiple comparison circuits can be set with different comparison values. By comparing the size of the driving current with the different comparison values ​​of each comparison circuit, the size of the current driving current can be determined; the output of each comparison circuit is then connected to the switch circuit in the internal resistance adjustment unit. By controlling the on and off of the corresponding switch circuit, the resistance value of the internal resistance adjustment unit can be adjusted.

[0067] Optionally, the processing circuit 112 may be a processor, which may control the on and off of the switch circuit in the internal resistance adjustment unit by comparing the magnitude of the driving current inside the processor and generating corresponding control instructions, thereby adjusting the resistance value of the internal resistance adjustment unit.

[0068] The specific structural details of the processing circuit 112 are not limited here and can be configured accordingly according to actual conditions.

[0069] As described above, the processing circuit 112 adjusts the internal resistance adjustment unit based on the current drive current. It can also be considered that the specific output of the internal resistance adjustment unit varies with the current drive current. For example, when the internal resistance adjustment unit is used to adjust the resistance of the current-limiting resistor, the greater the drive current, the smaller the resistance of the current-limiting resistor; the smaller the drive current, the larger the resistance of the current-limiting resistor. When the internal resistance adjustment unit is used to adjust the power supply of the light source driver, the greater the drive current, the greater the output power of the light source driver; the smaller the drive current, the smaller the output power of the light source driver.

[0070] Furthermore, the processing circuit 112 is further configured to determine the blood oxygen level based on the received signal of the receiving circuit. There is no limitation on the method for determining the blood oxygen level, and the method can be determined according to actual needs.

[0071] The blood oxygen measurement circuit provided in this embodiment provides an internal resistance adjustment unit in the driving circuit. The processing circuit adjusts the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit. That is, the internal resistance of the transistor in the transistor unit is adjusted so that the internal resistance of the transistor changes with the magnitude of the driving current. This allows the transistor to operate in a region with a small internal resistance change rate as much as possible within the entire driving current range, thereby reducing the noise of the blood oxygen driving circuit and, in turn, the noise of the entire blood oxygen measurement circuit.

[0072] As an optional implementation of this embodiment, Figure 4 As shown, the first end of the transistor is grounded via the internal resistance adjustment unit, and the processing circuit 112 is used to adjust the resistance value of the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit.

[0073] like Figure 4 As shown, the internal resistance adjustment unit is used as a current limiting resistor of the transistor. The processing circuit 112 adjusts the internal resistance adjustment unit based on the magnitude of the driving current, thereby adjusting the resistance value of the current limiting resistor of the transistor 104.

[0074] The internal resistance adjustment unit is connected to the first end of the transistor and used as the current limiting resistor of the transistor. The processing circuit can adjust the resistance value of the internal resistance adjustment unit so that the transistor operates in an area with a small internal resistance change rate, and the internal resistance of the transistor is adjusted by changing the resistance value of the current limiting resistor. The circuit structure is simple, easy to implement, and low in cost.

[0075] In some optional implementations of this embodiment, the internal resistance adjustment unit includes a resistor unit and a switch circuit unit. The resistor unit is connected to the first terminal of the transistor and serves as a current-limiting resistor for the transistor. The switch circuit unit is connected to the resistor unit and the processing circuit, respectively, and is configured to adjust the resistance value of the resistor unit based on a control signal from the processing circuit.

[0076] Specifically, the processing circuit 112 determines the resistance value of the resistor unit based on the current driving current, and generates a control signal based on the determined resistance value. The control signal is used to control the on / off switching of the switch circuit unit. The switch circuit unit adjusts the resistance value of the resistor unit by performing corresponding on / off operations based on the control signal.

[0077] Optionally, the resistance unit may include at least two resistors, and the switch circuit unit is connected in series or in parallel with at least one resistor. In this case, the resistance values ​​of the at least two resistors are not adjustable.

[0078] For example, Figure 5 As shown, the resistance unit includes two current-limiting resistors, namely current-limiting resistor 105 and current-limiting resistor 201, and the switch circuit unit is a switch circuit 202, which is connected in series with current-limiting resistor 201. Specifically, when switch circuit 202 is closed, current-limiting resistor 105 and current-limiting resistor 201 are connected in parallel, and the resistance value of the resistance unit is the resistance value of the current-limiting resistor 105 and current-limiting resistor 201 in parallel; when switch circuit 202 is opened, current-limiting resistor 201 is disconnected from the resistance unit, and the resistance value of the resistance unit is the resistance value of current-limiting resistor 105. Figure 5 In the internal resistance adjustment unit shown, when the switch circuit 202 is closed, the resistance value of the resistance unit is smaller than the resistance value of the resistance unit when the switch circuit 202 is open.

[0079] Based on this, when the driving current of the driving circuit increases, the processing circuit 112 can send a control signal to close the switch circuit 202, thereby connecting the current-limiting resistor 105 in parallel with the current-limiting resistor 201 to reduce the resistance value of the internal resistance adjustment unit. When the driving current of the driving circuit decreases, the processing circuit 112 can send a control signal to open the switch circuit 202, disconnecting the current-limiting resistor 201 from the resistance unit to increase the resistance value of the internal resistance adjustment unit. By changing the resistance value with the change of the driving current, the transistor operates in a region with a small resistance change rate under different driving currents.

[0080] like Figure 6As shown, the resistance unit includes a current-limiting resistor 401 and a current-limiting resistor 105, and a switch circuit 402 is connected in parallel with the current-limiting resistor 401. Specifically, when the switch circuit 402 is closed, the current-limiting resistor 401 is short-circuited, and the resistance value of the resistance unit is equal to the resistance value of the current-limiting resistor 105. When the switch circuit 402 is open, the current-limiting resistor 401 and the current-limiting resistor 105 are connected in series, and the resistance value of the resistance unit is equal to the resistance value of the current-limiting resistor 401 and the current-limiting resistor 105 connected in series. Therefore, the resistance value of the resistance unit after the switch circuit 402 is closed is less than the resistance value of the resistance unit after the switch circuit 402 is open.

[0081] Based on this, when the driving current of the driving circuit increases, the processing circuit 112 controls the switch circuit 402 to close to reduce the resistance value of the resistance unit; when the driving current of the driving circuit decreases, the processing circuit 112 controls the switch circuit 402 to open to increase the resistance value of the resistance unit. By changing the resistance value with the driving current, the transistor operates in a region with a small resistance change rate under different driving currents.

[0082] In some other optional implementations of this embodiment, the switch circuit unit is a selection switch unit, and each selection branch thereof is connected to the resistor of the resistance unit. Figure 7 As shown, the resistor unit includes n current limiting resistors, namely current limiting resistor 105 to current limiting resistor 302. Switch circuit 301 is a selection switch circuit, and each current limiting resistor is connected to each branch of the selection switch circuit.

[0083] Specifically, the processing circuit 112 controls the corresponding branch of the switch circuit 301 to be closed or opened according to the magnitude of the driving current, thereby adjusting the resistance value and number of the parallel-connected current-limiting resistors. Figure 7 The N current limiting resistors can be combined arbitrarily to achieve a suitable resistance value of the current limiting resistor to match the driving current.

[0084] As an optional implementation of this embodiment, Figure 8 As shown, the internal resistance adjustment unit can be a digital potentiometer 501. The digital potentiometer 501 is connected to the first end of the transistor and the processing circuit 112 respectively. The processing circuit 112 is used to generate a control signal based on the magnitude of the driving current of the driving circuit to adjust the resistance value of the digital potentiometer 501.

[0085] The resistance value is adjusted by using a digital potentiometer, which saves the use of switch circuit units, further simplifies the circuit structure and reduces the circuit volume.

[0086] In some optional implementations of this embodiment, the transistor unit includes a driving current control circuit and a first signal conditioning circuit. Figure 7As shown, the driving current control circuit 107 is connected to the processing circuit 112. The processing circuit 112 is used to determine the magnitude of the driving current based on the receiving signal of the receiving circuit, and control the driving current control circuit 107 to output a corresponding analog voltage signal.

[0087] The input end of the first signal conditioning circuit 106 is connected to the output end of the drive current control circuit 107, and the output end of the first signal conditioning circuit 106 is connected to the second end of the transistor 104. The second end of the transistor 104 can also be understood as the control end of the transistor 104. Furthermore, the first signal conditioning circuit 106 is used to process the analog voltage signal and output it to the transistor. The first signal conditioning circuit 106 outputs the control voltage of the transistor 104, thereby controlling the on-state internal resistance of the transistor, and the on-state internal resistance of the transistor is different at different drive currents. Specifically, the principle of the change in the on-state internal resistance of the transistor 104 is that the drive current control circuit 107 outputs different analog control signals at different drive currents, and its output signal acts on the first signal conditioning circuit 106, which then controls the on-state internal resistance of the transistor 104 through the first signal conditioning circuit 106.

[0088] like Figure 7 As shown, the third terminal of transistor 104 is connected to an analog switch circuit 103 in the light-emitting circuit. Analog switch circuit 103 is used to time-share control the light emission of light-emitting diode 101. Through analog switch circuit 103, light-emitting diodes with two different wavelengths can be connected to the circuit for driving, thereby achieving time-shared emission of two different light-emitting diodes. The two wavelengths of light-emitting diodes are red light-emitting diodes and infrared light-emitting diodes, respectively. Analog switch circuit 103 is also connected to a light source driver power supply 102, which is used to drive the light-emitting diodes.

[0089] As an optional implementation of this embodiment, the receiving circuit includes a receiving tube 108, an IV conversion circuit 109, a second signal conditioning circuit 110, and an ADC circuit 111. The receiving tube 108 is used to convert the optical signal into a current signal, the IV conversion circuit 109 is used to convert the current signal into a voltage signal, the second signal conditioning circuit 110 is used to convert the voltage signal into a voltage signal that meets ADC requirements, and the ADC circuit 111 is used to convert the analog signal into a digital signal.

[0090] Processing circuit 112 is used to process the digital signal output by the receiving circuit and, based on this signal, determine the magnitude of the transistor drive current to ultimately calculate blood oxygen levels. Processing circuit 112 is also used to adjust the internal resistance adjustment unit based on the magnitude of the drive current, so that the transistor operates in a region with a low internal resistance change rate. For example, if the internal resistance adjustment unit serves as the current-limiting resistor for transistor 104, processing circuit 112 determines the resistance value of the internal resistance adjustment unit based on the magnitude of the drive current.

[0091] The embodiment of the present invention further provides a blood oxygen measurement device, which includes a device body and a blood oxygen measurement circuit. The specific structural details of the blood oxygen measurement circuit are described above and will not be repeated here.

[0092] Specifically, the blood oxygen measurement circuit is housed within the device body. The device body may also include an area for the detection site. Light emitted by the light-emitting diode illuminates the detection site, while the receiving diode receives the light transmitted or reflected by the detection site. This light is then processed into an electrical signal by the processing circuit to obtain blood oxygen. During measurement, the processing circuit also adjusts the internal resistance adjustment unit based on the drive current, ensuring that the transistor operates within a region with minimal internal resistance change.

[0093] Further optionally, a display area may be provided on the blood oxygen measurement device to display the real-time measurement results of the blood oxygen level. Alternatively, other measurement results may be displayed, and the specific configuration may be made according to actual needs.

[0094] The blood oxygen measurement device provided in this embodiment provides an internal resistance adjustment unit in the driving circuit. The processing circuit adjusts the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit. That is, the internal resistance of the transistor in the transistor unit is adjusted so that the internal resistance of the transistor changes with the magnitude of the driving current. This allows the transistor to operate in a region with a small internal resistance change rate within the entire driving current range as much as possible, thereby reducing the noise of the blood oxygen driving circuit and, in turn, the noise of the blood oxygen measurement device.

[0095] The embodiment of the present invention further provides a blood oxygen measurement method, which is applied to the processing circuit of the above-mentioned blood oxygen measurement circuit. Figure 9 Said measuring method comprises:

[0096] S11, obtaining the magnitude of the driving current of the driving circuit.

[0097] The magnitude of the driving current of the driving circuit can be set by the processing circuit according to the default value, or it can be adjusted in real time by the processing circuit during the measurement process. There is no restriction on the way in which the processing circuit obtains the magnitude of the driving current. It is only necessary to ensure that the processing circuit can obtain the magnitude of the driving current of the driving circuit.

[0098] S12, adjusting the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit to adjust the internal resistance of the transistor in the transistor unit.

[0099] After obtaining the magnitude of the driving current of the driving circuit, the processing circuit adjusts the internal resistance adjustment unit according to the specific driving current, and then adjusts the internal resistance of the transistor in the transistor unit, so that under different driving currents, the transistors all operate in a region with a small internal resistance change rate, thereby reducing the noise of the entire blood oxygen measurement circuit and improving the accuracy of the measurement results.

[0100] The adjustment method of the internal resistance of the transistor in the transistor unit can be found in the above description and will not be repeated here.

[0101] S13, obtaining a first receiving signal from the receiving circuit.

[0102] The processing circuit acquires the first received signal of the receiving circuit in real time during the measurement process, and the first received signal is used to determine the blood oxygen.

[0103] S14: Determine blood oxygen based on the first received signal.

[0104] After obtaining the first received signal, the processing circuit can use it to calculate the blood oxygen level.

[0105] The blood oxygen measurement method provided in this embodiment adjusts the internal resistance of the transistor in the transistor unit so that the internal resistance of the transistor changes with the driving current. This allows the transistor to operate as close to the region of internal resistance change rate as possible within the entire driving current range, thereby reducing the noise of the blood oxygen drive circuit and, in turn, the noise of the entire blood oxygen measurement circuit, thereby improving the accuracy of the measurement results.

[0106] In some optional implementations of this embodiment, the above S11 may include the following steps:

[0107] (1) Obtain a second reception signal from the receiving unit.

[0108] (2) Determine the magnitude of the driving current based on the second received signal.

[0109] As described above, the drive current selected for the initial measurement is pre-set. Therefore, during the measurement process, the drive current needs to be adjusted in real time based on the actual blood oxygen measurement results. The actual blood oxygen measurement results are calculated using the second received signal of the receiving unit. If the blood oxygen level cannot be calculated using the initially set drive current for some reason, the drive current needs to be adjusted. Therefore, during the measurement process, the processing circuit also determines the drive current based on the second received signal of the receiving unit.

[0110] It should be noted that the first received signal and the second received signal refer to the same signal sent by the receiving circuit to the processing circuit. This distinction is used for descriptive purposes only and does not constitute a substantive difference. That is, during blood oxygen measurement, the processing circuit calculates the blood oxygen value based on the received signal (i.e., the first received signal or the second received signal) and determines whether the current drive current is appropriate. If not, the drive current is adjusted, and the internal resistance adjustment unit is adjusted accordingly.

[0111] The blood oxygen measurement method provided in this embodiment uses the received signal to control the magnitude of the driving current, so that the driving current can meet the measurement requirements, thereby improving the accuracy of the measurement.

[0112] In a specific application example of this embodiment, combined with Figure 7 The measurement circuit shown above can be described as follows:

[0113] After powering on the blood oxygen measurement device, it first initializes and then checks whether the blood oxygen sensor is connected. If the blood oxygen sensor is not connected, it continues to check whether the sensor is connected. If the blood oxygen sensor is connected, the processing circuit sends a drive signal to the drive current control circuit 107 and selects one or more current-limiting resistors based on the set current threshold. If the current threshold 1 is met, current-limiting resistor 1 is selected; if the current threshold n is met, current-limiting resistor n is selected. Similarly, the processing circuit then determines whether the received second signal meets the measurement requirements. If not, the driving current is adjusted, the current-limiting resistor is selected, and the measurement is repeated. If the requirements are met, the blood oxygen level is calculated based on this data.

[0114] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A blood oxygen measurement circuit, characterized in that: include: light-emitting tube; receiving circuit; A driving circuit comprising a transistor unit and an internal resistance adjustment unit, wherein the internal resistance adjustment unit is connected to the transistor unit; a processing circuit, connected to the receiving circuit and the internal resistance adjustment unit, respectively, the processing circuit being configured to adjust the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit to adjust the internal resistance of the transistor in the transistor unit, and to determine the blood oxygen measurement result based on the received signal of the receiving circuit, wherein the driving current is the current flowing through the light-emitting diode, the transistor, and the internal resistance adjustment unit; Wherein, when the driving current decreases, the resistance value of the internal resistance adjustment unit is increased; when the driving current increases, the resistance value of the internal resistance adjustment unit is decreased.

2. The blood oxygen measurement circuit according to claim 1, characterized in that: The first end of the transistor is grounded through the internal resistance adjustment unit, and the processing circuit is used to adjust the resistance value of the internal resistance adjustment unit based on the magnitude of the driving current of the driving circuit.

3. The blood oxygen measurement circuit according to claim 2, characterized in that: The internal resistance adjustment unit includes: a resistance unit connected to the first end of the transistor; A switch circuit unit is connected to the resistance unit and the processing circuit respectively, and the switch circuit is used to adjust the resistance value of the resistance unit based on a control signal sent by the processing circuit.

4. The blood oxygen measurement circuit according to claim 3, characterized in that: The resistance unit includes at least two resistors, and the switch circuit unit is connected in series or in parallel with at least one of the resistors.

5. The blood oxygen measurement circuit according to claim 4, characterized in that: The switch circuit unit is a selection switch unit, and each selection branch of the selection switch unit is connected to the resistor in the resistor unit respectively.

6. The blood oxygen measurement circuit according to claim 4, characterized in that: The at least two resistors are connected in parallel, and the switch circuit unit includes at least one switch, and the switch is connected in series with the resistors; or, The at least two resistors are connected in series, and the switch circuit unit includes at least one switch, which is connected in parallel with the resistors.

7. The blood oxygen measurement circuit according to claim 2, characterized in that: The internal resistance adjustment unit includes a digital potentiometer, and the digital potentiometer is connected to the first end of the transistor and the processing circuit respectively.

8. The blood oxygen measurement circuit according to claim 1, characterized in that: include: A light-emitting circuit having the light-emitting tube; The internal resistance adjustment unit is a variable voltage driving source, which is connected to the light emitting circuit and is used to drive the light emitting tube to emit light.

9. The blood oxygen measurement circuit according to any one of claims 1 to 8, characterized in that: The transistor unit further includes: a driving current control circuit connected to the processing circuit, the processing circuit being further configured to determine the magnitude of the driving current based on a received signal from the receiving circuit, and to control the driving current control circuit to output a corresponding analog voltage signal; A signal conditioning circuit, the input end of which is connected to the output end of the drive current control circuit, the output end of which is connected to the second end of the transistor, and the signal conditioning circuit is used to process the analog voltage signal and output it to the transistor.

10. A blood oxygen measurement device, characterized in that: include: Equipment body; The blood oxygen measurement circuit according to any one of claims 1 to 9, wherein the blood oxygen measurement circuit is arranged in the device body.

11. A blood oxygen measurement method, characterized in that: The method is applied to the processing circuit of the blood oxygen measurement circuit according to any one of claims 1 to 9, and the method includes: Obtaining the magnitude of the driving current of the driving circuit; adjusting the internal resistance adjusting unit based on the magnitude of the driving current of the driving circuit to adjust the internal resistance of the transistor in the transistor unit; Acquire a first received signal from the receiving circuit; Blood oxygen is determined based on the first received signal.

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