Micropower pickup circuit

Abstract

The utility model relates to a micropower pickup circuit, which comprises a self-excitation booster circuit, a voltage stabilization booster circuit, an energy storage circuit, a discharge drive circuit and a single chip microcomputer chip, the self-excitation booster circuit is connected with an input voltage, and an output end of the self-excitation booster circuit is connected with an input end of the voltage stabilization booster circuit. The output end of the voltage stabilizing and boosting circuit is connected with the input end of the energy storage circuit, the output end of the energy storage circuit is connected with the input end of the discharging driving circuit, the single-chip microcomputer chip is connected with the output end of the discharging driving circuit, and the single-chip microcomputer chip is connected with the energy storage circuit and monitors the output voltage of the energy storage circuit. And if the output voltage of the energy storage circuit is greater than or equal to the preset voltage, the single-chip microcomputer chip acquires a signal value and performs signal transmission. According to the technical scheme, extremely-low-power pickup is effectively achieved, pickup and sending of multiple signals in the physical world can be achieved through self-adjustment of a single-chip microcomputer software system under the condition that human intervention is not needed, and therefore the application range of the Internet of Things world is widened.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of internet of things monitoring technology especially relates to a micro -power pickup circuit. BACKGROUND

[0002] The current boost integrated circuit, the lowest can reach 0.5V input, namely 500mV. Can improve output voltage through the frequency conversion boost mode, satisfy the power supply demand of subsequent integrated circuit, also can reach the energy pickup integrated circuit of 150mV or so of extremely low power. 500mV conventional voltage boost chip, cannot satisfy the pickup scene of extremely low power, the requirement of energy input still exists the limiting condition, the IC that can reach 150mV or so extremely low power on the market at present, first input demand is not low enough, secondly this kind of chip usually all need a 550mV voltage cold start condition, and the lead time is long, the price is high. SUMMARY

[0003] The utility model provides a micro -power pickup circuit aims at solving the problem of high cost of existing boost integrated circuit, and input power is not low enough.

[0004] The utility model provides a micro -power pickup circuit, including self -excited boost circuit, voltage stabilizing boost circuit, energy storage circuit, discharge drive circuit and singlechip chip, the self -excited boost circuit inserts input voltage, the output of self -excited boost circuit is connected with the input of voltage stabilizing boost circuit, the output of voltage stabilizing boost circuit is connected with the input of energy storage circuit, the output of energy storage circuit is connected with the input of discharge drive circuit, singlechip chip is connected with the output of discharge drive circuit, singlechip chip is connected with energy storage circuit and monitors the output voltage of energy storage circuit, if the output voltage of energy storage circuit is greater than or equal to preset voltage, then singlechip chip gathers signal value and carries out signal transmission.

[0005] As a further improvement of the utility model, the self-excitation voltage boosting circuit includes external power supply, transformer T1, field effect tube Q1, voltage stabilizing diode D1 and voltage stabilizing diode D2, the positive pole of external power supply is connected with the left end of transformer T1, the negative pole of external power supply is grounded, one end of the left end of transformer T1 is connected with external power supply, the drain of field effect tube Q1 is connected with the left end of transformer T1, the source of field effect tube Q1 is grounded, the gate of field effect tube Q1 is connected with one end of resistance R1, the other end of resistance R1 is grounded, one end of capacitor C3 is connected with the gate of field effect tube Q1, the other end of capacitor C3 is connected with one end of capacitor C2, one end of capacitor C2 is connected with the right end of transformer T1, the other end of capacitor C2 is connected with the positive pole of voltage stabilizing diode D1, the negative pole of voltage stabilizing diode D1 is connected with voltage stabilizing voltage boosting circuit, the negative pole of voltage stabilizing diode D2 is connected with the other end of capacitor C2, the positive pole of voltage stabilizing diode D2 is grounded, and the transformation ratio of transformer T1 is 1:100.

[0006] As a further improvement of the utility model, the voltage stabilizing voltage boosting circuit includes voltage stabilizing chip U1, inductor L1 and voltage stabilizing diode D3, one end of inductor L1 is connected with the negative pole of voltage stabilizing diode D1, the other end of inductor L1 is connected with the positive pole of voltage stabilizing diode D3, the negative pole of voltage stabilizing diode D3 is connected with the energy storage circuit, the 1 and 5 pins of voltage stabilizing chip U1 are connected at the two ends of inductor L1 respectively, the 2 pin of voltage stabilizing chip U1 is grounded, the 3 pin of voltage stabilizing chip U1 is connected with one end of capacitor C5, the other end of capacitor C5 is connected with the negative pole of voltage stabilizing diode D3, the 4 pin of voltage stabilizing chip U1 is connected with one end of resistance R2, and the other end of resistance R2 is connected with one end of inductor L1.

[0007] As a further improvement of the utility model, one end of resistance R3 is connected with the negative pole of voltage stabilizing diode D3, the other end of resistance R3 is connected with one end of resistance R4, and the other end of resistance R4 is grounded.

[0008] As a further improvement of the utility model, the energy storage circuit includes energy storage chip U4 and storage battery GB1, the 4 pin of energy storage chip U4 is connected with the negative pole of voltage stabilizing diode D3, the 2 pin of energy storage chip U4 is grounded, the 5 pin of energy storage chip U4 is connected with one end of resistance R5, the other end of resistance R5 is grounded, the 3 pin of energy storage chip U4 is connected with the 1 pin of storage battery GB1, the 2 pin of storage battery GB1 is grounded, the single-chip microcomputer chip is connected with the 1 pin of storage battery GB1, and VBAT voltage is detected.

[0009] As a further improvement of the utility model, the energy storage circuit further includes light emitting diode D6, the negative pole of light emitting diode D6 is connected with the 1 pin of energy storage chip U4, the positive pole of light emitting diode D6 is connected with one end of resistance R13, the other end of resistance R13 is connected with the 4 pin of energy storage chip U4.

[0010] As a further improvement of the utility model, the energy storage circuit further includes a capacitor C7, a positive pole of the capacitor C7 is connected with a 4th pin of the energy storage chip U4, and a negative pole of the capacitor C7 is grounded.

[0011] As a further improvement of the utility model, the discharge driving circuit includes a linear voltage stabilizer U2, a 1st pin and a 3rd pin of the linear voltage stabilizer U2 are connected with a 1st pin of the storage battery GB1, a 2nd pin of the linear voltage stabilizer U2 and one end of a capacitor C9 are grounded, the other end of the capacitor C9 is connected with the 1st pin of the storage battery GB1, and a 5th pin of the linear voltage stabilizer U2 is connected with a voltage input pin of the single-chip microcomputer chip.

[0012] As a further improvement of the utility model, the discharge driving circuit further includes capacitors C8, C10 and C11, a positive pole of the capacitor C11 is connected with the 5th pin of the linear voltage stabilizer U2, a positive pole of the capacitor C8 is connected with the 5th pin of the linear voltage stabilizer U2, one end of the capacitor C10 is connected with the 5th pin of the linear voltage stabilizer U2, and a negative pole of the capacitor C8, a negative pole of the capacitor C11 and the other end of the capacitor C10 are grounded.

[0013] As a further improvement of the utility model, the 5th pin of the linear voltage stabilizer U2 is connected with the 5th pin of an operational amplifier U9, a 1st pin of the operational amplifier U9 is connected with one end of a resistor R88, the other end of the resistor R88 is connected with the 1st pin of the storage battery GB1, one end of a resistor R89 is connected with the 1st pin of the operational amplifier U9, the other end of the resistor R89 is grounded, a 3rd pin and a 4th pin of the operational amplifier U9 are connected with one end of a resistor R86, the other end of the resistor R86 is connected with an ADC input end of the single-chip microcomputer chip, a DO output end of the single-chip microcomputer chip is connected with one end of a resistor R67, the other end of the resistor R67 is connected with a gate of a field effect transistor Q3A, a drain of the field effect transistor Q3A is connected with a gate of a field effect transistor Q3B, a source of the field effect transistor Q3A is grounded, a source of the field effect transistor Q3B is connected with the 5th pin of the linear voltage stabilizer U2, and a drain of the field effect transistor Q3B outputs a 3.3V voltage.

[0014] The utility model discloses the beneficial effect is: effectively realize the pickup of extremely low power, and through the self -adjustment of singlechip software system, can not need the case of human intervention, realize the pickup and send of many signals of physical world, thereby enhance the application scope of the internet of things world. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the connection relation diagram of each circuit of the utility model;

[0016] Figure 2 It is the circuit connection drawing of the self -excitation boost circuit and the voltage stabilizing boost circuit of the utility model;

[0017] Figure 3 is the circuit connection diagram of the energy storage circuit and the discharge driving circuit of the utility model;

[0018] Figure 4 is the circuit connection diagram of the single-chip chip part of the utility model. DETAILED DESCRIPTION

[0019] In order to make the utility model's purpose, technical scheme and advantage more clearly, the following is combined with the drawing and example, and the utility model is further detailed.

[0020] The utility model provides a kind of micro-power pickup circuit, including self-excitation boost circuit, voltage stabilizing boost circuit, energy storage circuit, discharge driving circuit and single-chip, the self-excitation boost circuit is connected input voltage, the output of the self-excitation boost circuit is connected with the input of the voltage stabilizing boost circuit, the output of the voltage stabilizing boost circuit is connected with the input of the energy storage circuit, the output of the energy storage circuit is connected with the input of the discharge driving circuit, the single-chip is connected with the output of the discharge driving circuit, the single-chip is connected with the energy storage circuit and monitors the output voltage of the energy storage circuit, if the output voltage of the energy storage circuit is greater than or equal to preset voltage, the single-chip acquires signal value and carries out signal transmission.

[0021] The utility model provides a kind of micro-power pickup circuit, adopts domestic conventional material and device, can greatly reduce input voltage acquisition to 20mV-50mV interval range under the premise of sacrificing part efficiency, this makes very small solar panel can pass ordinary sunlight, even indoor light, can be used as energy input. So it can meet the physical signal pickup in the world of Internet of Things, various extreme environments, without external energy supply, realize self-sufficiency.

[0022] As an embodiment of the utility model, the self-excitation boost circuit includes external power supply, transformer T1, field effect tube Q1, voltage stabilizing diode D1 and voltage stabilizing diode D2, the positive pole of external power supply is connected with the left end of transformer T1, the negative pole of external power supply is grounded, one end of the left end of transformer T1 is connected with external power supply, the drain of field effect tube Q1 is connected with the left end of transformer T1, the source of field effect tube Q1 is grounded, the gate of field effect tube Q1 is connected with one end of resistance R1, the other end of resistance R1 is grounded, one end of capacitor C3 is connected with the gate of field effect tube Q1, the other end of capacitor C3 is connected with one end of capacitor C2, one end of capacitor C2 is connected with the right end of transformer T1, the other end of capacitor C2 is connected with the positive pole of voltage stabilizing diode D1, the negative pole of voltage stabilizing diode D1 is connected with voltage stabilizing boost circuit, the negative pole of voltage stabilizing diode D2 is connected with the other end of capacitor C2, the positive pole of voltage stabilizing diode D2 is grounded.

[0023] As another embodiment of the utility model, the transformer T1 is 1:100.

[0024] The self-excitation boost circuit can realize the conversion of 1:100 of the input source with extremely low power through the transformer T1, and realize the preliminary boost conversion of direct current to alternating current through the self-excitation circuit composed of the resistor R1, the capacitor C3 and the field effect tube Q1. The input source of 20-50 mV can be changed to the primary voltage output of 2-5 V as the input source of the next stage circuit.

[0025] The working principle of the self-excitation boost circuit is that in the moment of turning on the power supply, the weak current generated by the primary coil of the transformer T1 is coupled to the secondary coil through the transformer, and the specific frequency signal is loaded to the gate stage of the field effect tube Q1 through the frequency selection network of the secondary coil of the transformer T1 and the capacitor C3. Due to the feedback of the same name end of the transformer T1, the feedback is gradually strengthened, and finally stabilizes. The oscillation frequency is determined by the secondary winding inductance of the transformer T1 and the capacitor C3. In the formula, L is the inductance value of the secondary winding of the transformer T1, and C is the capacitance value of the capacitor C3. The alternating voltage generated by the secondary winding of the transformer T1 is rectified into direct current voltage through the voltage stabilizing diode D1 and the voltage stabilizing diode D2 and is provided to the next stage circuit.

[0026] As another embodiment of the utility model, the voltage stabilizing boost circuit comprises a voltage stabilizing chip U1, an inductor L1 and a voltage stabilizing diode D3, one end of the inductor L1 is connected with the negative electrode of the voltage stabilizing diode D1, the other end of the inductor L1 is connected with the positive electrode of the voltage stabilizing diode D3, the negative electrode of the voltage stabilizing diode D3 is connected with the energy storage circuit, the 1 and 5 pins of the voltage stabilizing chip U1 are respectively connected at both ends of the inductor L1, the 2 pin of the voltage stabilizing chip U1 is grounded, the 3 pin of the voltage stabilizing chip U1 is connected with one end of the capacitor C5, the other end of the capacitor C5 is connected with the negative electrode of the voltage stabilizing diode D3, the 4 pin of the voltage stabilizing chip U1 is connected with one end of the resistor R2, the other end of the resistor R2 is connected with one end of the inductor L1.

[0027] As another embodiment of the utility model, one end of the resistor R3 is connected with the negative electrode of the voltage stabilizing diode D3, the other end of the resistor R3 is connected with one end of the resistor R4, and the other end of the resistor R4 is grounded.

[0028] The energy output after the self-excitation boost circuit can be used as the input source of the voltage stabilizing boost circuit, and this part can be realized by using conventional devices, so that the voltage can be relatively stably controlled at 5 V.

[0029] The working principle of the voltage stabilizing boost circuit is divided into two main stages:

[0030] The first main stage is switch on state: when the switch tube in the power control voltage stabilizing chip U1 is turned on, the power voltage charges the inductor L1, and the voltage polarity of the two ends of the inductor L1 is left positive and right negative.

[0031] The second main stage is switch off state: when the switch tube in the power control voltage stabilizing chip U1 is turned off, the voltage polarity of the two ends of the inductor L1 is right positive and left negative, the voltage stabilizing diode D3 is turned on, the inductor L1 is discharged, the input voltage and the voltage on the inductor L1 are superposed, the capacitor C6 is charged and supplies power to the load circuit, and the output voltage gradually increases.

[0032] The resistor R3, the resistor R4 and the capacitor C5 are sampling circuits, when the output voltage deviates from 5V, the output voltage can be stabilized at 5V by continuously switching the on and off states of the switch tube.

[0033] As another embodiment of the utility model, the energy storage circuit includes energy storage chip U4 and storage battery GB1, the 4th pin of energy storage chip U4 is connected with the negative electrode of voltage stabilizing diode D3, the 2nd pin of energy storage chip U4 is grounded, the 5th pin of energy storage chip U4 is connected with one end of resistor R5, the other end of resistor R5 is grounded, the 3rd pin of energy storage chip U4 is connected with the 1st pin of storage battery GB1, the 2nd pin of storage battery GB1 is grounded, the single-chip microcomputer chip is connected with the 1st pin of storage battery GB1, and the VBAT voltage is detected.

[0034] As another embodiment of the utility model, the energy storage circuit further includes light emitting diode D6, the negative electrode of light emitting diode D6 is connected with the 1st pin of energy storage chip U4, the positive electrode of light emitting diode D6 is connected with one end of resistor R13, and the other end of resistor R13 is connected with the 4th pin of energy storage chip U4.

[0035] As another embodiment of the utility model, the energy storage circuit further includes capacitor C7, the positive electrode of capacitor C7 is connected with the 4th pin of energy storage chip U4, and the negative electrode of capacitor C7 is grounded.

[0036] The purpose of converting the voltage stabilizing and boosting circuit into 5V voltage is to accumulate energy for the storage battery GB1 of the next stage, and the energy can be accumulated continuously for a long time, so that the single working demand of the system can be met.

[0037] The working principle of the energy storage circuit is as follows: the energy storage chip U4 is a linear charge and discharge management device, 5V voltage is charged to the storage battery through the power transistor inside the chip in constant current and constant voltage, the charging current can be programmed and set by the external resistor R5, the resistor R13 and the light emitting diode D6 form a charging indication circuit, when the input voltage is greater than the low voltage detection threshold of the power supply, the energy storage chip U4 starts to charge the storage battery GB1, the 1 pin of the energy storage chip U4 outputs low level, indicating that the charging is in progress, if the voltage of the storage battery GB1 is lower than 3V, the energy storage chip U4 charges the storage battery with a small current in pre-charging mode, when the voltage of the battery is higher than 3V, the energy storage chip U4 charges the battery in constant current mode, when the voltage of the battery approaches 4.2V, the charging current gradually decreases, and the energy storage chip U4 enters the constant voltage charging mode, when the charging current decreases to the charging end threshold, the charging period ends, and the 1 pin of the energy storage chip U4 outputs high resistance state.

[0038] As another embodiment of the utility model, the discharge driving circuit includes a linear voltage regulator U2, the 1 and 3 pins of the linear voltage regulator U2 are connected with the 1 pin of the storage battery GB1, the 2 pin of the linear voltage regulator U2 and one end of the capacitor C9 are grounded, the other end of the capacitor C9 is connected with the 1 pin of the storage battery GB1, and the 5 pin of the linear voltage regulator U2 is connected with the voltage input pin of the single-chip microcomputer chip.

[0039] As another embodiment of the utility model, the discharge driving circuit further includes capacitors C8, C10 and C11, the positive pole of the capacitor C11 is connected with the 5 pin of the linear voltage regulator U2, the positive pole of the capacitor C8 is connected with the 5 pin of the linear voltage regulator U2, one end of the capacitor C10 is connected with the 5 pin of the linear voltage regulator U2, and the negative pole of the capacitor C8, the negative pole of the capacitor C11 and the other end of the capacitor C10 are grounded.

[0040] The discharge driving circuit provides conventional and sufficient energy for subsequent single-chip microcomputer chip work. The working principle of the discharge driving circuit is as follows: the discharge driving circuit uses a low-dropout linear voltage regulator U2, which is internally provided with a negative feedback sampling and adjusting circuit, an error amplification circuit and a transistor adjusting circuit, when the input voltage is high or low, the negative feedback sampling and adjusting circuit sends the voltage collected from the output to the error amplification circuit, and then adjusts the conduction degree of the transistor, so that the output voltage is stabilized at 3.3V; when the output load changes and causes the output voltage to rise or fall, through the above-mentioned negative feedback mechanism, the output voltage can be stabilized at 3.3V, thereby providing stable power supply driving for the subsequent circuit.

[0041] As another embodiment of the utility model, the 5th pin of linear voltage stabilizer U2 is connected with the 5th pin of operational amplifier U9, the 1st pin of operational amplifier U9 is connected with one end of resistor R88, the other end of resistor R88 is connected with the 1st pin of battery GB1, one end of resistor R89 is connected with the 1st pin of operational amplifier U9, the other end of resistor R89 is grounded, the 3rd and 4th pins of operational amplifier U9 are connected with one end of resistor R86, the other end of resistor R86 is connected with the ADC input end of single-chip microcomputer chip, the DO output end of single-chip microcomputer chip is connected with one end of resistor R67, the other end of resistor R67 is connected with the gate of field effect tube Q3A, the drain of field effect tube Q3A is connected with the gate of field effect tube Q3B, the source of field effect tube Q3A is grounded, the source of field effect tube Q3B is connected with the 5th pin of linear voltage stabilizer U2, and the drain of field effect tube Q3B outputs 3.3V voltage.

[0042] The single-chip microcomputer chip monitors the output voltage VBAT of the energy storage circuit part, collects the voltage of the energy storage battery in real time, and determines whether there is enough energy for system operation. The operational amplifier U9 is connected with the 1st pin of battery GB1 through the resistor divider network composed of resistor R88 and resistor R89, accesses the VBAT voltage for detection, and accesses the single-chip microcomputer chip from the ADC input interface of the single-chip microcomputer chip. The peripheral circuit composed of field effect tube Q3A and field effect tube Q3B outputs 3.3V voltage to the external circuit under the control of the single-chip microcomputer chip. The single-chip microcomputer chip can select model GD32F103CBT6 or GD32F303RCT6.

[0043] The working process of the circuit is as follows: the self-excited boost circuit, the voltage stabilizing boost circuit and the energy storage circuit continuously store energy for battery GB1 until the stored energy can provide the minimum energy consumption required for starting the single-chip microcomputer chip; when the single-chip microcomputer can start smoothly, first detect the value of VBAT in the circuit, determine whether the voltage value meets the preset voltage value, if it meets, the normal system operation can be realized, the required signal value is collected and signal transmission is carried out, and the demand of Internet of Things in various industries is realized; if the VBAT value does not meet the preset voltage value, the current value is saved, the single-chip microcomputer chip wake-up time is adjusted, and the low-power sleep mode is continued, and the next start is waited. Through self-adjustment of the wake-up time, finally the effective balance of dynamic charging time and wake-up working time is achieved.

[0044] The scheme can effectively realize extremely low power pickup by sacrificing part of the efficiency, and can realize pickup and sending of many signals of the physical world without human intervention through self-adjustment of the single-chip microcomputer software system, thereby enhancing the application scope of the Internet of Things world, such as outdoor forest fire prevention sensor signal collection and sending, monitoring of various outdoor well covers, outdoor gas meter reading, etc., and is suitable for various scenes requiring low signal collection frequency.

[0045] The above is a further detailed description of the utility model in combination with specific preferred embodiments, and the specific implementation of the utility model cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the utility model belongs, without departing from the concept of the utility model, a number of simple deductions or substitutions can be made, and all of them should be regarded as belonging to the protection scope of the utility model.

Claims

1. A micro-power pickup circuit, characterized by comprising: The self-excitation voltage-boosting circuit, the voltage-stabilizing voltage-boosting circuit, the energy storage circuit, the discharge driving circuit and the single-chip microcomputer chip are connected in series.

2. The micro-power pickup circuit according to claim 1, characterized by, The self-excitation voltage-boosting circuit comprises an external power supply, a transformer T1, a field effect transistor Q1, a voltage-stabilizing diode D1 and a voltage-stabilizing diode D2.

3. The micro-power pickup circuit of claim 2, wherein, The voltage-stabilizing voltage-boosting circuit comprises a voltage-stabilizing chip U1, an inductor L1 and a voltage-stabilizing diode D3.

4. The micro-power pickup circuit according to claim 3, characterized by, One end of a resistor R3 is connected to the negative electrode of the voltage-stabilizing diode D3, and the other end of the resistor R3 is connected to one end of a resistor R4.

5. The micropower pickup circuit of claim 3, wherein, The energy storage circuit comprises an energy storage chip U4 and a storage battery GB1.

6. The micropower pickup circuit of claim 5, wherein, The energy storage circuit further comprises a light emitting diode D6, the negative electrode of the light emitting diode D6 is connected with the 1 pin of the energy storage chip U4, the positive electrode of the light emitting diode D6 is connected with one end of the resistor R13, and the other end of the resistor R13 is connected with the 4 pin of the energy storage chip U4.

7. The micro-power pickup circuit of claim 5, wherein, The energy storage circuit further comprises a capacitor C7, the positive electrode of the capacitor C7 is connected with the 4 pin of the energy storage chip U4, and the negative electrode of the capacitor C7 is grounded.

8. The micropower pickup circuit of claim 5, wherein, The discharge driving circuit comprises a linear voltage regulator U2, the 1 pin and the 3 pin of the linear voltage regulator U2 are connected with the 1 pin of the battery GB1, the 2 pin of the linear voltage regulator U2 is connected with one end of the capacitor C9, the other end of the capacitor C9 is connected with the 1 pin of the battery GB1, and the 5 pin of the linear voltage regulator U2 is connected with the voltage input pin of the single-chip microcomputer chip.

9. The micropower pickup circuit of claim 8, wherein, The discharge driving circuit further comprises a capacitor C8, a capacitor C10 and a capacitor C11, the positive electrode of the capacitor C11 is connected with the 5 pin of the linear voltage regulator U2, the positive electrode of the capacitor C8 is connected with the 5 pin of the linear voltage regulator U2, one end of the capacitor C10 is connected with the 5 pin of the linear voltage regulator U2, and the negative electrode of the capacitor C8, the negative electrode of the capacitor C11 and the other end of the capacitor C10 are grounded.

10. The micro-power pickup circuit of claim 8, wherein, The 5 pin of the linear voltage regulator U2 is connected with the 5 pin of the operational amplifier U9, one end of the resistor R88 is connected with the 1 pin of the operational amplifier U9, the other end of the resistor R88 is connected with the 1 pin of the battery GB1, one end of the resistor R89 is connected with the 1 pin of the operational amplifier U9, the other end of the resistor R89 is grounded, the 3 pin and the 4 pin of the operational amplifier U9 are connected with one end of the resistor R86, the other end of the resistor R86 is connected with the ADC input end of the single-chip microcomputer chip, the DO output end of the single-chip microcomputer chip is connected with one end of the resistor R67, the other end of the resistor R67 is connected with the gate electrode of the field effect transistor Q3A, the drain electrode of the field effect transistor Q3A is connected with the gate electrode of the field effect transistor Q3B, the source electrode of the field effect transistor Q3A is grounded, the source electrode of the field effect transistor Q3B is connected with the 5 pin of the linear voltage regulator U2, and the drain electrode of the field effect transistor Q3B outputs a 3.3V voltage.

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