Reference voltage providing type heart rate monitoring circuit based on pulse type gain buffer

Abstract

The invention discloses a reference voltage providing type heart rate monitoring circuit based on a pulse type gain buffer, which comprises a front-back stage isolation type reference voltage supply module, an amplification module, an infrared emitter, a control type transceiving power supply module, an infrared receiver and a power supply, the first output end of the power supply supplies power to the input end of the front-back stage isolation type reference voltage supply module, the output end of the front-back stage isolation type reference voltage supply module is connected to the non-inverting input end of the amplification module, and the inverting input end of the amplification module is connected to the output end of the infrared receiver. The first output end of the power supply supplies power to the infrared transmitter and the infrared receiver through the control type transceiving power supply module, and the front-and-back-stage isolation type reference voltage supply module is used for providing reference voltage for the amplification module. The reference voltage providing type heart rate monitoring circuit based on the pulse type gain buffer solves the problem that in the prior art, reference voltage is not connected to the inverted input end of an amplifier U2A.

Description

Technical Field

[0001] This invention relates to the field of heart rate monitoring circuits, and more specifically to a heart rate monitoring circuit based on a pulse-type gain buffer reference voltage. Background Technology

[0002] Chinese patent disclosure discloses a heart rate and pulse detector driving control circuit based on an STC microcontroller, application number CN201921860898.4. This STC microcontroller-based heart rate and pulse detector driving control circuit includes a central control module, a power switch interface module, a reset circuit module, a crystal oscillator circuit module, a data transmission module, an LCD1602 liquid crystal display circuit module, a heart rate and pulse pickup circuit module, a voice prompt module, and an information storage module. The voice prompt module is connected to the output terminal of the control module, the power switch interface module and the reset circuit module are connected to the input terminal of the control module, and the heart rate and pulse pickup circuit module, the information storage module, the crystal oscillator circuit module, and the LCD1602 liquid crystal display circuit module are connected to the data input and output terminals of the central control module.

[0003] Although the STC microcontroller-based heart rate and pulse detector driver control circuit can detect heart rate through pulse, it still has the following drawback: the inverting input of amplifier U2A is not connected to a reference voltage, which causes the signal after amplifier U2A to fail to meet the requirements of subsequent AD sampling. Summary of the Invention

[0004] The present invention provides a heart rate monitoring circuit based on a pulse-type gain buffer reference voltage, which solves the problem in the prior art that the amplifier U2A has no reference voltage connected to its inverting input terminal.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses a heart rate monitoring circuit based on a pulse-type gain buffer reference voltage supply, comprising: a pre- and post-stage isolated reference voltage supply module, an amplification module, an infrared transmitter, a controllable transceiver power supply module, an infrared receiver, and a power supply. The first output terminal of the power supply supplies power to the input terminal of the pre- and post-stage isolated reference voltage supply module. The output terminal of the pre- and post-stage isolated reference voltage supply module is connected to the non-inverting input terminal of the amplification module, and the inverting input terminal of the amplification module is connected to the output terminal of the infrared receiver. The first output terminal of the power supply supplies power to the infrared transmitter and the infrared receiver through the controllable transceiver power supply module. The pre- and post-stage isolated reference voltage supply module is used to provide a reference voltage to the amplification module.

[0006] Preferably, the isolated reference voltage supply module includes: a voltage divider supply unit, a grounded voltage regulator unit, and a unity-gain buffer. The input terminal of the voltage divider supply unit is connected to the first output terminal of the power supply, the output terminal of the voltage divider supply unit is connected to the non-inverting input terminal of the unity-gain buffer, the inverting input terminal of the unity-gain buffer is connected to the output terminal of the unity-gain buffer, the inverting input terminal of the unity-gain buffer is connected to the output terminal of the grounded voltage regulator unit, and the output terminal of the unity-gain buffer is the output terminal of the isolated reference voltage supply module. The unity-gain buffer is used to isolate the output terminal of the voltage divider supply unit from the output terminal of the amplification module.

[0007] Preferably, the high-voltage end of the controllable transceiver power supply module is connected to the first output end of the power supply, the low-voltage end of the controllable transceiver power supply module is connected to the anode of the infrared transmitter, the cathode of the infrared transmitter is connected to the anode of the infrared receiver, the cathode of the infrared receiver is the output end of the infrared receiver, and the cathode of the infrared receiver is grounded through the first load.

[0008] Preferably, the high-voltage end of the controllable transceiver power supply module is connected to the first output end of the power supply, the low-voltage end of the controllable transceiver power supply module is connected to the anode of the infrared transmitter and the anode of the infrared receiver, the cathode of the infrared receiver is the output end of the infrared receiver, and the cathode of the infrared receiver is grounded through the first load.

[0009] Preferably, the cathode of the infrared emitter is connected to the output of the unity-gain buffer.

[0010] Preferably, the cathode of the infrared emitter is connected to the output of the unity-gain buffer via a current-limiting unit.

[0011] Preferably, the output terminal of the isolated reference voltage supply module and the input terminal of the amplification module are connected via a controllable switch module. The control terminal of the controllable switch module is connected to the low-voltage terminal of the controllable transceiver power supply module or the output terminal of a constant voltage output buck module. The input terminal of the constant voltage output buck module is connected to the low-voltage terminal of the controllable transceiver power supply module. The constant voltage output buck module is used to turn on the controllable switch module only when the low-voltage terminal of the controllable transceiver power supply module outputs a voltage.

[0012] Compared with the prior art, the present invention has the following beneficial effects: In this application, firstly, in order to ensure that the amplification module has a certain amplification ratio, a front-to-back isolated reference voltage supply module is designed, which provides a 2.5V reference voltage to the non-inverting input terminal of the amplification module. Then, a front-to-back isolated reference voltage supply module was designed with front-to-back isolation function, which isolates the voltage signal input near the first output terminal of the power supply from the amplification module, thereby achieving front-to-back isolation. At the same time, the front-to-back isolated reference voltage supply module also meets the requirements of high input impedance and low output impedance. The design of the unity-gain buffer in the front-to-back isolated reference voltage supply module means that the reference voltage supply module is no longer the existing technology of connecting a resistor to divide the voltage after the voltage is input to output the reference voltage (this existing technology is the same as R10 and R9 in the heart rate and pulse detector drive control circuit based on STC microcontroller in application number: CN201921860898.4). Instead, a unity-gain buffer is used to achieve two-stage isolation between the output terminal of the voltage divider supply unit and the amplification module. This avoids the output terminal of the voltage divider supply unit being directly connected to the non-inverting input terminal of the amplification module, avoids the second load change in the amplification module affecting the reference voltage supply, and ensures that the non-inverting input terminal of the amplification module is always connected to 2.5V during operation, avoiding the influence on the first amplified signal obtained by the amplification module and improving the accuracy of the first amplified signal.

[0013] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of the front-to-back isolated reference voltage supply module, amplification module, infrared transmitter, control transceiver power supply module, and infrared receiver in one embodiment.

[0015] Figure 2 This is a circuit diagram of the front-to-back isolated reference voltage supply module, amplification module, infrared transmitter, control transceiver power supply module, and infrared receiver in another embodiment.

[0016] Figure 3 This is a circuit diagram of the front-to-back isolated reference voltage supply module, amplification module, infrared transmitter, control transceiver power supply module, and infrared receiver in another embodiment.

[0017] Figure 4 This is a circuit diagram of the front-to-back isolated reference voltage supply module, amplification module, infrared transmitter, control transceiver power supply module, and infrared receiver in another embodiment.

[0018] Figure 5This is the circuit diagram for a constant voltage output step-down module. Detailed Implementation

[0019] To make the technical means, creative features, objectives, and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments: like Figures 1 to 3 As shown, this invention discloses a heart rate monitoring circuit based on a pulse-type gain buffer reference voltage supply, comprising: a pre- and post-stage isolated reference voltage supply module, an amplification module, an infrared transmitter D2, a controllable transceiver power supply module, an infrared receiver D3, and a power supply. The first output terminal of the power supply supplies power to the input terminal of the pre- and post-stage isolated reference voltage supply module. The output terminal of the pre- and post-stage isolated reference voltage supply module is connected to the non-inverting input terminal of the amplification module, and the inverting input terminal of the amplification module is connected to the output terminal of the infrared receiver D3. The first output terminal of the power supply supplies power to the infrared transmitter D2 and the infrared receiver D3 through the controllable transceiver power supply module. The pre- and post-stage isolated reference voltage supply module provides a reference voltage to the amplification module. In terms of physical layout, the infrared receiver D3 is positioned opposite the infrared transmitter D2, enabling the infrared receiver D3 to receive the infrared light reflected back from the wrist pulse after being emitted by the infrared transmitter D2.

[0020] For example, since different electrical components in the pre- and post-stage isolated reference voltage supply module, amplification module, infrared transmitter D2, control transceiver power supply module, infrared receiver D3, and control module require different voltages, the first output terminal of the power supply outputs 5V and the second output terminal of the power supply outputs 3.3V.

[0021] In this application, the pre- and post-stage isolated reference voltage supply module includes: a voltage divider supply unit, a grounded voltage regulator unit, and a unity-gain buffer U1. The input terminal of the voltage divider supply unit is connected to the first output terminal of the power supply. The output terminal of the voltage divider supply unit is connected to the non-inverting input terminal of the unity-gain buffer U1. The inverting input terminal of the unity-gain buffer U1 is connected to the output terminal of the unity-gain buffer U1. The inverting input terminal of the unity-gain buffer U1 is connected to the output terminal of the grounded voltage regulator unit. The output terminal of the unity-gain buffer U1 is the output terminal of the pre- and post-stage isolated reference voltage supply module. The unity-gain buffer U1 is used to isolate the voltage divider supply unit from the output terminal of the amplification module.

[0022] For example, the voltage divider supply unit includes resistors R1 and R2. The first terminal of resistor R1 is the input terminal of the voltage divider supply unit, and the second terminal of resistor R1 is the output terminal. The second terminal of resistor R1 is grounded through resistor R2. The voltage divided by resistors R1 and R2 provides voltage to the non-inverting input terminal of the unity-gain buffer. The output voltage of the voltage divider supply unit can be adjusted by designing the resistance values ​​of resistors R1 and R2.

[0023] For example, the grounded voltage regulator unit includes: capacitor C1, the first terminal of capacitor C1 is the output terminal of the grounded voltage regulator unit, and the second terminal of capacitor C1 is grounded. Capacitor C1 mainly functions as a voltage regulator, and different models of positive and negative terminals are used for capacitor C1.

[0024] For example, the unity-gain buffer U1 can be an OPA656 chip or an AD9630 chip, etc.

[0025] In summary, the voltage divider supply unit provides the input voltage to the non-inverting input of the unity-gain buffer U1, and the grounded voltage regulator stabilizes the inverting input of the unity-gain buffer U1, so that the output of the unity-gain buffer U1 can output a constant voltage, avoiding the output voltage of the unity-gain buffer U1 due to the change of the second load in the amplifier module, and avoiding mutual interference between the front and rear stages.

[0026] To enable the controlled transceiver power supply module to power the infrared receiver D3 and the infrared transmitter D2, two transceiver power supply methods are designed: the first transceiver power supply method and the second transceiver power supply method.

[0027] like Figure 1 As shown, the first power supply method for transmitting and receiving is as follows: the high-voltage end of the controllable transceiver power supply module is connected to the first output terminal of the power supply, the low-voltage end of the controllable transceiver power supply module is connected to the anode of infrared transmitter D2, the cathode of infrared transmitter D2 is connected to the anode of infrared receiver D3, the cathode of infrared receiver D3 is the output terminal of infrared receiver D3, and the cathode of infrared receiver D3 is grounded through the first load. The controllable transceiver power supply module can simultaneously control the operation of infrared receiver D3 and infrared transmitter D2. In this method, a portion of the current through infrared transmitter D2 flows to infrared transmitter D2, resulting in a higher current in infrared transmitter D2.

[0028] like Figure 2As shown, the second power supply method is as follows: the high-voltage end of the controllable transceiver power supply module is connected to the first output terminal of the power supply, and the low-voltage end of the controllable transceiver power supply module is connected to the anode of infrared transmitter D2 and the anode of infrared receiver D3. The cathode of infrared receiver D3 is the output terminal of infrared receiver D3, and the cathode of infrared receiver D3 is grounded through the first load. The controllable transceiver power supply module can simultaneously control the operation of infrared receiver D3 and infrared transmitter D2. In this method, the current through infrared transmitter D2 will not flow to infrared transmitter D2, and the current through infrared transmitter D2 will not pass through infrared transmitter D2, thus meeting the requirement of low current for infrared transmitter D2.

[0029] For example, the controlled transceiver power supply module has two implementation methods, namely a first controlled transceiver implementation method and a second controlled transceiver implementation method.

[0030] like Figure 1 As shown, the first controlled transceiver implementation method is as follows: The controlled transceiver power supply module includes a resistor R5 and a transistor Q1. The first end of the resistor R5 is the high-voltage terminal of the controlled transceiver power supply module, the second end of the resistor R5 is connected to the anode of an indicator light D1, the cathode of the indicator light D1 is connected to the collector of the transistor Q1, the emitter of the transistor Q1 is the low-voltage terminal of the controlled transceiver power supply module, and the base of the transistor Q1 is the control terminal of the controlled transceiver power supply module. The control terminal of the controlled transceiver power supply module is connected to the output terminal of the control module. Under the control of the control module, the controlled transceiver power supply module supplies power to the infrared transmitter D2 and the infrared receiver D3. The resistor R5, the indicator light D1, and the transistor Q1 are connected in series to supply power to the infrared transmitter D2 and the infrared receiver D3. Infrared transmitter D2 and infrared receiver D3 are connected in parallel. When the resistance of infrared receiver D3 changes due to changes in the received light intensity, the resistance of infrared transmitter D2 and infrared receiver D3 changes after being connected in parallel. This causes a change in the low-voltage terminal voltage of the control transceiver power supply module, which in turn causes a change in the resistance of infrared receiver D3. This change is not only due to the change in the resistance of infrared receiver D3 itself, but also related to the parallel-connected infrared transmitter D2. In order to ensure that the resistance of infrared receiver D3 is proportional to its own resistance, a second control transceiver implementation method is designed.

[0031] Preferably, transistor Q1 can be either an NPN transistor or a PNP transistor.

[0032] like Figure 3As shown, the second controlled transceiver implementation method is as follows: The controlled transceiver power supply module includes a transistor Q1. The collector of transistor Q1 is the high-voltage terminal of the controlled transceiver power supply module, and the emitter of transistor Q1 is the low-voltage terminal of the controlled transceiver power supply module. The low-voltage terminal of the controlled transceiver power supply module is connected to the anode of an indicator light D1, and the cathode of indicator light D1 is connected to the anode of an infrared emitter D2. Transistor Q1 acts as a switch. The resistance between the collector and emitter of transistor Q1 is very small and can be ignored. With this design, it is equivalent to: after transistor Q1 is powered on, the anode of indicator light D1 and infrared receiver D3 are directly connected to the first output terminal of the power supply. When infrared receiver D3 senses the change in infrared intensity, its resistance changes, but this does not change the voltage at the first output terminal of the power supply. This ensures that the voltage at infrared transmitter D2 remains the same and is not affected by the change in the resistance of infrared receiver D3. Therefore, the light intensity emitted by infrared transmitter D2 will not change arbitrarily. This achieves both the control of infrared receiver D3 and infrared transmitter D2, and ensures that the light intensity emitted by infrared transmitter D2 does not change arbitrarily.

[0033] To stabilize the cathode voltage of infrared emitter D2, the cathode of infrared emitter D2 is connected to the output of unity-gain buffer U1. This ensures that the cathode voltage of infrared emitter D2 is a constant 2.5V, while the output of unity-gain buffer U1 is simultaneously stabilized by a grounded voltage regulator.

[0034] like Figure 4 As shown, when the cathode of infrared transmitter D2 is connected to the anode of infrared receiver D3, the cathode of infrared transmitter D2 is connected to the output of unity-gain buffer U1 through a current-limiting unit. The current-limiting unit restricts backflow of current.

[0035] To ensure the amplifier module connects to the unity-gain buffer U1 output only after the infrared transmitter D2 is operational, a controllable switch module connects the output of the pre- and post-stage isolated reference voltage supply module to the input of the amplifier module. The control terminal of this controllable switch module is connected to either the low-voltage side of a controllable transceiver power supply module or the output of a constant-voltage output buck module. The input of the constant-voltage output buck module is connected to the low-voltage side of the controllable transceiver power supply module. This constant-voltage output buck module activates the controllable switch module only when the low-voltage side of the controllable transceiver power supply module outputs a voltage. This ensures the amplifier module connects to the unity-gain buffer U1 output only after the infrared transmitter D2 is operational, reducing power consumption. Furthermore, the controllable switch module automatically activates the non-inverting input of the amplifier module to connect to the unity-gain buffer U1 output only after the infrared transmitter D2 is lit.

[0036] For example, the constant voltage output buck module includes: comparator U3, resistor R7, and resistor R8. The first output terminal of the power supply is connected to the power supply terminal of comparator U3 and the first terminal of resistor R7. The second terminal of resistor R7 is grounded through resistor R8 and connected to the inverting input terminal of comparator U3. The non-inverting input terminal of comparator U3 is the input terminal of the constant voltage output buck module, and the output terminal of comparator U3 is the output terminal of the constant voltage output buck module. Resistors R7 and R8 divide the voltage output from the first output terminal of the power supply and supply it to the inverting input terminal of comparator U3, giving comparator U3 a comparison basis. When the low-voltage terminal of the controllable transceiver power supply module outputs a voltage, the voltage at the low-voltage terminal of the controllable transceiver power supply module is higher than the voltage at the second terminal of resistor R7. Comparator U3 outputs a high level, causing the controllable switch module to close.

[0037] For example, to achieve a high-level output from comparator U3 that closes the controllable switch module, the controllable switch module includes an NMOS transistor Q3. The drain of NMOS transistor Q3 is connected to the output of the unity-gain buffer U1, the source of NMOS transistor Q3 is connected to the input of the amplifier module, and the gate of NMOS transistor Q3 serves as the control terminal of the controllable switch module. Of course, when the comparator U3 outputs a low level that opens the controllable switch module, Q3 can be a PMOS transistor.

[0038] For example, such as Figure 5 As shown, the amplification module includes: resistor R3, resistor R4, capacitor C2, and amplifier U2. The first terminal of resistor R3 is the input terminal of the amplification module. The second terminal of resistor R3 is connected to the non-inverting input terminal of amplifier U2. The inverting input terminal of amplifier U2 is also the input terminal of the amplification module. The inverting input terminal of amplifier U2 is connected to the first terminal of resistor R4 and the first terminal of capacitor C2. The output terminal of amplifier U2 is connected to the second terminal of resistor R4 and the second terminal of capacitor C2. The output terminal of amplifier U2 is the output terminal of the amplification module. Of course, the amplification module may also include amplifiers and other components, as long as the amplification function can be achieved.

[0039] like Figures 1 to 4 As shown, the first load includes resistor R6, with its first terminal connected to the cathode of the infrared receiver tube and its second terminal grounded. Of course, the first load can also include other resistors.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A heart rate monitoring circuit based on a pulse-type gain buffer reference voltage, characterized in that, include: The system includes a pre- and post-stage isolated reference voltage supply module, an amplifier module, an infrared transmitter, a controllable transceiver power supply module, an infrared receiver, and a power supply. The first output of the power supply provides power to the input of the pre- and post-stage isolated reference voltage supply module. The output of the pre- and post-stage isolated reference voltage supply module is connected to the non-inverting input of the amplifier module, and the inverting input of the amplifier module is connected to the output of the infrared receiver. The first output of the power supply provides power to the infrared transmitter and the infrared receiver through the controllable transceiver power supply module. The pre- and post-stage isolated reference voltage supply module is used to provide a reference voltage to the amplifier module.

2. The heart rate monitoring circuit based on pulse-type gain buffer reference voltage as described in claim 1, characterized in that, The isolated reference voltage supply module includes a voltage divider supply unit, a grounded voltage regulator unit, and a unity-gain buffer. The input of the voltage divider supply unit is connected to the first output of the power supply. The output of the voltage divider supply unit is connected to the non-inverting input of the unity-gain buffer. The inverting input of the unity-gain buffer is connected to the output of the unity-gain buffer. The inverting input of the unity-gain buffer is connected to the output of the grounded voltage regulator unit. The output of the unity-gain buffer is the output of the isolated reference voltage supply module. The unity-gain buffer is used to isolate the output of the voltage divider supply unit from the output of the amplifier module.

3. The heart rate monitoring circuit based on a pulse-type gain buffer reference voltage as described in claim 2, characterized in that, The high-voltage end of the controllable transceiver power supply module is connected to the first output end of the power supply, the low-voltage end of the controllable transceiver power supply module is connected to the anode of the infrared transmitter, the cathode of the infrared transmitter is connected to the anode of the infrared receiver, the cathode of the infrared receiver is the output end of the infrared receiver, and the cathode of the infrared receiver is grounded through the first load.

4. The heart rate monitoring circuit based on pulse-type gain buffer reference voltage as described in claim 3, characterized in that, The high-voltage end of the controllable transceiver power supply module is connected to the first output end of the power supply, and the low-voltage end of the controllable transceiver power supply module is connected to the anode of the infrared transmitter and the anode of the infrared receiver. The cathode of the infrared receiver is the output end of the infrared receiver, and the cathode of the infrared receiver is grounded through the first load.

5. The heart rate monitoring circuit based on a pulse-type gain buffer reference voltage as described in claim 4, characterized in that, The cathode of the infrared emitter is connected to the output of the unity-gain buffer.

6. The heart rate monitoring circuit based on a pulse-type gain buffer reference voltage as described in claim 5, characterized in that, The cathode of the infrared emitter is connected to the output of the unity-gain buffer via a current-limiting unit.

7. The heart rate monitoring circuit based on a pulse-type gain buffer reference voltage as described in claim 5 or 6, characterized in that, The output of the pre- and post-stage isolated reference voltage supply module is connected to the input of the amplification module via a controllable switch module. The control terminal of the controllable switch module is connected to the low-voltage terminal of the controllable transceiver power supply module or the output terminal of a constant voltage output buck module. The input terminal of the constant voltage output buck module is connected to the low-voltage terminal of the controllable transceiver power supply module. The constant voltage output buck module is used to turn on the controllable switch module only when the low-voltage terminal of the controllable transceiver power supply module outputs a voltage.

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