Electroencephalogram signal acquisition circuit suitable for electroencephalogram signals
By introducing BIAS driver circuit, electrostatic protection circuit and voltage stabilization source power supply circuit into the EEG signal acquisition circuit, the problems of insufficient anti-interference ability and high noise are solved, and efficient and low-power EEG signal acquisition is achieved, suitable for Portable brain-computer interface application.
Patent Information
- Application Number
- CN202411350051.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2024-12-13
AI Technical Summary
The existing EEG signal acquisition technology has problems such as insufficient anti-interference ability, high noise, large power consumption, and inconvenience, making it difficult to effectively collect and analyze weak and random EEG signals.
An EEG signal acquisition circuit including A/D conversion circuit and electrostatic protection circuit was designed. The BIAS drive circuit was used to reduce the industrial frequency interference, the electrostatic protection circuit enhanced the anti-static ability, and achieved low power supply through the voltage-regulating source and battery charging circuit. Power consumption and portability.
It realizes efficient acquisition of EEG signals, reduces noise, enhances anti-interference ability, extends battery life, ensures battery safety and stable performance, and is suitable for portable brain-computer interface applications.
Smart Images
Figure CN119112213A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electroencephalogram signal acquisition, and in particular relates to an electroencephalogram signal acquisition circuit suitable for electroencephalogram signals. Background Art
[0002] The acquisition of EEG signals is one of the important means to study brain activity. Currently, the common EEG signal acquisition technologies mainly include EEG acquisition, cortical EEG acquisition, depth electrode acquisition and functional magnetic resonance imaging.
[0003] EEG acquisition is to record the activity of neurons in the cerebral cortex by placing electrodes on the scalp. This method is relatively cheap and portable, and is the most common neuroimaging method in brain-computer interface (BCI) research. The acquisition process includes placing electrodes on the surface of the scalp, usually fixed with glue or a cap to ensure good contact between the electrodes and the scalp to reduce electromagnetic interference and muscle activity interference with the signal. The advantage is that it is non-invasive and can provide information on the activity patterns of the brain in different states, such as sleep, wakefulness, cognitive task execution, etc., and can be used to diagnose and monitor some brain diseases.
[0004] EEG acquisition involves surgically implanting electrodes on the surface of the brain to record electrical activity. Compared with EEG, EEG has better spatial resolution and can accurately detect high-frequency brain activity that EEG cannot capture. The EEG acquisition process requires neurosurgery to implant electrodes and is usually used before epilepsy surgery or for severely disabled patients.
[0005] Deep electrode acquisition is also surgically implanted into the brain to record the electrical activity of neurons. This method is similar to electrocorticography, but it records the activity from a small group of neurons, providing a different picture of brain activity. Deep electrode acquisition also requires neurosurgery and is mainly used for epilepsy surgery or other medical needs.
[0006] Although MRI cannot directly measure electrical activity, it can be used to measure changes in cerebral blood flow associated with different mental activities. MRI systems require strong magnetic fields, so they are expensive and not portable. They are mainly used to study brain function and structure, rather than to monitor brain activity in real time.
[0007] EEG acquisition is widely used because of its non-invasiveness and relatively low cost. The EEG signal is the sum of the postsynaptic potentials of the cerebral cortex neurons recorded on the cerebral cortex or scalp surface. It contains a large amount of physiological and pathological information and is a very typical bioelectric signal. The EEG signal can be divided into different brain waves according to the frequency and amplitude of the signal. Brain waves are easily affected by a person's physiological condition and mainly reflect the electrical activity characteristics of the brain. However, the EEG signal is a highly random non-stationary signal with a very weak amplitude and a frequency range of 0.5~50HZ. Generally, the scalp signal is only about 50μV, and it can be regarded as noise if it exceeds ±100μV. Summary of the invention
[0008] In view of the above problems, the present invention proposes an EEG signal acquisition circuit suitable for EEG signals, which has strong anti-interference ability, extremely low equivalent input noise, as well as the advantages of low power consumption, modular functions, and portability.
[0009] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions: The present invention provides an electroencephalogram signal acquisition circuit suitable for electroencephalogram signals, including an A / D conversion circuit and an electrostatic protection circuit; The A / D conversion circuit includes an A / D conversion chip, a BIAS driving circuit and a routing circuit; The input end of the electrostatic protection circuit is used to connect to the data acquisition electrode of the EEG cap, and the output end thereof is respectively connected to the corresponding N input pins on the A / D conversion chip; The reference pin SRB2 of the A / D conversion chip is used to connect to the reference electrode of the EEG cap, and is also connected to each N input pin of the A / D conversion chip through the routing circuit; The input end of the BIAS driving circuit is connected to the ground electrode of the EEG cap, and the output end thereof is respectively connected to the bias driving output pin, the bias driving input pin and the bias driving in-phase input pin on the A / D conversion chip.
[0010] Optionally, the BIAS driving circuit includes a first resistor, a second resistor and a first capacitor; One end of the first resistor serves as the input end of the BIAS driving circuit, and the other end thereof is respectively connected to the bias driving output pin and the bias driving input pin on the A / D conversion chip, and is also respectively connected to one end of the second resistor and the first capacitor; The second resistor and the other end of the first capacitor are connected to each other and then connected to the bias drive in-phase input pin on the A / D conversion chip.
[0011] Optionally, the routing circuit includes a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor and a ninth capacitor; One end of the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, the sixth capacitor, the seventh capacitor, the eighth capacitor and the ninth capacitor is respectively connected to the reference pin SRB2 of the A / D conversion chip, and the other end is respectively connected to the corresponding N input pin on the A / D conversion chip.
[0012] Optionally, the electrostatic protection circuit includes a first surge protection chip, a second surge protection chip, a third surge protection chip, a fourth surge protection chip, and a fifth surge protection chip that are independent of each other; The four data transmission pins of the first surge protection chip are respectively connected to the P1 pin to the P4 pin of the A / D conversion chip; The four data transmission pins of the second surge protection chip are respectively connected to the P5 pin to the P8 pin of the A / D conversion chip; The four data transmission pins of the third surge protection chip are respectively connected to the input end of the BIAS driving circuit of the A / D conversion chip, and the 6N input pin to the 8N input pin; The four data transmission pins of the fourth surge protection chip are respectively connected to the 2N input pin to the 5N input pin of the A / D conversion chip; The two data transmission pins of the fifth surge protection chip are respectively connected to the 1N input pin and the reference pin of the A / D conversion chip.
[0013] Optionally, the EEG signal acquisition circuit further includes a voltage stabilizer power supply circuit; the voltage stabilizer power supply circuit includes a voltage stabilizer, a switch, a first linear voltage stabilizer, a second linear voltage stabilizer, a DC-DC power supply conversion chip and a third linear voltage stabilizer; The switch is connected to a voltage stabilizing source; The input end of the first linear regulator is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator and the DC-DC power conversion chip, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip is connected to the input end of the third linear regulator, and the output end of the third linear regulator is connected to the corresponding power supply pin on the A / D conversion chip.
[0014] Optionally, the first linear regulator receives the 5V voltage output by the switch and outputs a 3.3V digital voltage; The 3.3V digital voltage is sent to the power supply pin of the A / D conversion chip that requires a 3.3V digital voltage, and also serves as the input of the second linear regulator and the DC-DC power conversion chip. When the 3.3V digital voltage is used as the input of the second linear regulator, the second linear regulator outputs a 2.5V analog voltage, and the 2.5V analog voltage is sent to the power supply pin of the A / D conversion chip that requires a 2.5V analog voltage. When the 3.3V digital voltage is used as the input of the DC-DC power conversion chip, the DC-DC power conversion chip outputs an analog -3.3V analog voltage. The -3.3V analog voltage is used as the input of the third linear regulator, and the third linear regulator outputs an analog -2.5V analog voltage, which is sent to the power supply pin of the A / D conversion chip that requires a -2.5V analog voltage.
[0015] Optionally, the EEG signal acquisition circuit further includes a battery power supply circuit, and the battery power supply circuit includes a battery, a slide switch, a first linear regulator, a second linear regulator, a DC-DC power supply conversion chip and a third linear regulator; The slide switch is connected to a battery; The input end of the first linear regulator is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator and the DC-DC power conversion chip, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip is connected to the input end of the third linear regulator, and the output end of the third linear regulator is connected to the corresponding power supply pin on the A / D conversion chip.
[0016] Optionally, the EEG signal acquisition circuit further includes a battery charging circuit, and an output end of the battery charging circuit is connected to the first pin of the sliding switch; The sliding switch comprises a first pin, a second pin and a third pin; When the slide switch slides to the third pin, the battery power supply circuit is powered on, and the EEG signal acquisition circuit starts to work; When the slide switch slides to the first pin, the battery power supply circuit is closed and the battery stops working.
[0017] Optionally, the battery charging circuit includes a USB charging interface and a charging protection chip; The input end of the USB charging interface is used for external power supply, and the output end is connected to the charging protection chip; The charging pin of the charging protection chip is connected to the first pin of the sliding switch.
[0018] Optionally, when the external ambient temperature is greater than a set temperature threshold or the charging power is greater than a set power threshold, the thermal feedback in the charging protection chip adjusts the charging current to reduce the temperature of the charging protection chip. At the same time, the charging protection chip has a battery reverse connection protection function. When the battery is reversely connected, the charging protection chip will shut down and display a fault status with no charging current. After the reverse-connected battery is correctly connected, the charging protection chip automatically starts the charging cycle.
[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention designs the right leg driving function of the A / D conversion chip to form a right leg driving circuit (ie, BIAS driving circuit), which can effectively reduce the influence of power frequency interference and acquisition signals.
[0020] The present invention has an electrostatic protection circuit for protecting the EEG signal acquisition circuit, and uses the N terminal as a single-ended input to connect the reference electrode of the AD conversion chip with the reference electrode on the EEG cap, so that the collected EEG signal can be directly analyzed after reference without re-referencing.
[0021] The present invention proposes a charging protection chip to extend the life of the battery and ensure the safety and stability of the performance of the battery.
[0022] The present invention proposes a battery charging circuit. If it is just a simple battery circuit, the circuit will stop working when the battery is out of power, and the battery must be unplugged and charged before working again. However, with the design of the battery charging circuit, the battery can be charged directly, and using the USB interface, it can be charged directly through a computer, which reduces the test time and avoids the battery suddenly stopping working due to power failure during long-term testing, which affects the test efficiency and consistency of the results. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor, among which: Figure 1 This is a schematic diagram of the principle of an EEG signal acquisition circuit according to an embodiment of the present invention; Figure 2 A circuit diagram of an A / D conversion circuit according to an embodiment of the present invention; Figure 3 A circuit diagram of an electrostatic protection circuit according to an embodiment of the present invention; Figure 4A circuit diagram of a voltage-stabilizing source power supply circuit according to an embodiment of the present invention; Figure 5 A circuit diagram of a battery charging circuit according to an embodiment of the present invention; Figure 6 A circuit diagram of a battery power supply circuit according to an embodiment of the present invention Figure 7 This is a signal acquisition diagram of an EEG signal acquisition circuit according to an embodiment of the present invention. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0025] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may also include different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.
[0026] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0027] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0028] The application principle of the present invention is described in detail below in conjunction with the accompanying drawings.
[0029] The present invention provides an electroencephalogram signal acquisition circuit suitable for electroencephalogram signals, such as Figure 1 As shown, it includes an A / D conversion circuit and an electrostatic protection circuit; The A / D conversion circuit includes an A / D conversion chip, a BIAS driving circuit and a routing circuit; The input end of the electrostatic protection circuit is used to connect to the data acquisition electrode of the EEG cap, and the output end thereof is respectively connected to the corresponding N input pins on the A / D conversion chip; The reference pin SRB2 of the A / D conversion chip is used to connect to the reference electrode of the EEG cap, and is also connected to each N input pin of the A / D conversion chip through the routing circuit; The input end of the BIAS driving circuit is connected to the ground electrode of the EEG cap, and the output end thereof is respectively connected to the bias driving output pin, the bias driving input pin and the bias driving in-phase input pin on the A / D conversion chip.
[0030] In the present invention, the 8 IN input pins on the A / D conversion chip are used as input terminals to connect the data acquisition electrodes of the EEG cap, and the reference electrode SRB2 on the A / D conversion chip is connected to the reference electrode of the EEG cap, which can effectively reduce noise, and in order to reduce power frequency interference, a BIAS driving circuit is also designed to eliminate power frequency interference. In order to prevent the A / D conversion chip from being damaged by high-voltage and high-current electrostatic discharge, and damage to the circuit caused by human electrostatic breakdown, an electrostatic protection circuit is also added to the front end of the channel input in the present invention to enhance the tolerance of the EEG signal acquisition circuit to electrostatic discharge.
[0031] In a specific embodiment of the present invention, Figure 2 As shown, the A / D conversion chip is the U5 chip in the figure; in the specific implementation process, the A / D conversion chip can be selected from the ADS1299 chip; the BIAS driving circuit includes a first resistor R13, a second resistor R12 and a first capacitor C16; One end of the first resistor R13 is used as the input end of the BIAS driving circuit, and the other end thereof is respectively connected to the bias driving output pin (BIASOUT) and the bias driving input pin (BIASIN) on the A / D conversion chip, and is also respectively connected to the second resistor R12 and one end of the first capacitor C16; The second resistor R12 and the other end of the first capacitor C16 are connected to each other and then connected to the bias drive in-phase input pin (BIASREF) on the A / D conversion chip.
[0032] In a specific embodiment of the present invention, Figure 2 As shown, the routing circuit includes a second capacitor C17, a third capacitor C18, a fourth capacitor C19, a fifth capacitor C20, a sixth capacitor C21, a seventh capacitor C22, an eighth capacitor C23 and a ninth capacitor C24; One end of the second capacitor C17, the third capacitor C18, the fourth capacitor C19, the fifth capacitor C20, the sixth capacitor C21, the seventh capacitor C22, the eighth capacitor C23 and the ninth capacitor C24 is respectively connected to the reference pin SRB2 of the A / D conversion chip, and the other end is respectively connected to the corresponding input pins (8N, 7N, 6N, 5N, 4N, 3N, 2N, 1N) on the A / D conversion chip; Based on the above design, the reference electrode of the AD conversion chip (i.e. Figure 2 The SRB2 pin in the EEG cap is connected to the reference electrode on the EEG cap, so that the collected EEG signal can be directly analyzed without re-referencing.
[0033] In a specific embodiment of the present invention, Figure 3 As shown, the electrostatic protection circuit includes a first surge protection chip U8, a second surge protection chip U6, a third surge protection chip U7, a fourth surge protection chip U9, and a fifth surge protection chip U10 which are independent of each other; The four data transmission pins (i.e., IO1-IO4 pins) of the first surge protection chip U8 are respectively connected to the P1 pin to the P4 pin of the A / D conversion chip; The four data transmission pins (i.e., IO1-IO4 pins) of the second surge protection chip U6 are respectively connected to the P5 pin to the P8 pin of the A / D conversion chip; The four data transmission pins (i.e., IO1-IO4 pins) of the third surge protection chip U7 are respectively connected to the input end (BIAS) of the BIAS driving circuit of the A / D conversion chip, and the 6N input pin-8N input pin; The four data transmission pins (i.e., IO1-IO4 pins) of the fourth surge protection chip U9 are respectively connected to the 2N input pin - 5N input pin of the A / D conversion chip; The two data transmission pins (i.e., IO1-IO4 pins) of the fifth surge protection chip U10 are respectively connected to the 1N input pin and the reference pin (SRB2) of the A / D conversion chip; The present invention has an electrostatic protection circuit for protecting the brain electric signal collection circuit.
[0034] In a specific embodiment of the present invention, Figure 4 As shown, the EEG signal acquisition circuit also includes a voltage stabilizer power supply circuit; the voltage stabilizer power supply circuit includes a voltage stabilizer, a switch J3, a first linear voltage stabilizer U1, a second linear voltage stabilizer U2, a DC-DC power supply conversion chip U3 and a third linear voltage stabilizer U4; The switch J3 is connected to a voltage stabilizing source; The input end of the first linear regulator U1 is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator U2 and the DC-DC power conversion chip U3, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator U2 is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip U3 is connected to the input end of the third linear regulator U4, and the output end of the third linear regulator U4 is connected to the corresponding power supply pin on the A / D conversion chip.
[0035] The first linear regulator U1 receives the 5V voltage output by the switch J3 and outputs a 3.3V digital voltage; The 3.3V digital voltage is sent to the power supply pin of the A / D conversion chip U5 that requires a 3.3V digital voltage, and also serves as the input of the second linear regulator U2 and the DC-DC power conversion chip U3. When the 3.3V digital voltage is used as the input of the second linear regulator U2, the second linear regulator U2 outputs a 2.5V analog voltage, and the 2.5V analog voltage is sent to the power supply pin of the A / D conversion chip that requires a 2.5V analog voltage. When the 3.3V digital voltage is used as the input of the DC-DC power conversion chip U3, the DC-DC power conversion chip U3 outputs a -3.3V analog voltage, and the -3.3V voltage is used as the input of the third linear regulator U4. The third linear regulator U4 outputs a -2.5V analog voltage, which is given to the power supply pin of the A / D conversion chip U5 that requires a -2.5V analog voltage.
[0036] In a specific embodiment of the present invention, Figure 5 As shown, the EEG signal acquisition circuit also includes a battery power supply circuit, which includes a battery, a slide switch J1, a first linear regulator U1, a second linear regulator U2, a DC-DC power conversion chip U3 and a third linear regulator U4; The slide switch J1 is connected to the battery; The input end of the first linear regulator U1 is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator U2 and the DC-DC power conversion chip U3, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator U2 is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip U3 is connected to the input end of the third linear regulator U4, and the output end of the third linear regulator U4 is connected to the corresponding power supply pin on the A / D conversion chip.
[0037] The first linear regulator U1 receives the 5V voltage output by the slide switch J1 and outputs a 3.3V digital voltage; The 3.3V digital voltage is sent to the power supply pin of the A / D conversion chip U5 that requires a 3.3V digital voltage, and also serves as the input of the second linear regulator U2 and the DC-DC power conversion chip U3. When the 3.3V digital voltage is used as the input of the second linear regulator U2, the second linear regulator U2 outputs a 2.5V analog voltage, and the 2.5V analog voltage is sent to the power supply pin of the A / D conversion chip that requires a 2.5V analog voltage. When the 3.3V digital voltage is used as the input of the DC-DC power conversion chip U3, the DC-DC power conversion chip U3 outputs a -3.3V analog voltage, and the -3.3V voltage is used as the input of the third linear regulator U4. The third linear regulator U4 outputs a -2.5V analog voltage, which is given to the power supply pin of the A / D conversion chip U5 that requires a -2.5V analog voltage.
[0038] The present invention can select an external voltage stabilizer to input voltage to the voltage stabilizer power supply circuit, and then power the A / D conversion chip through the voltage stabilizer power supply circuit, or use an external battery to input voltage to power the A / D conversion chip. The main purpose of selecting a voltage stabilizer to power the A / D conversion chip is to facilitate debugging, observe the current change at any time, and avoid damage to the circuit caused by device abnormality. The analog power supply of the A / D conversion chip adopts ±2.5V, and the digital power supply adopts 3V.
[0039] The present invention adopts an external 5V battery to supply power to the battery circuit. The battery power supply is mainly small in size, easy to carry, and convenient for debugging and application outside the laboratory.
[0040] In a specific embodiment of the present invention, Figure 5 and 6 As shown, the EEG signal acquisition circuit also includes a battery charging circuit, and the output end of the battery charging circuit is connected to the first pin of the sliding switch J1; The slide switch J1 includes a first pin (i.e. Figure 5 Pin 1 in the Figure 5 Pin 2) and the third pin (i.e. Figure 5 Pin 3 in the jack); When the slide switch J1 slides to the third pin, the battery power supply circuit is powered on, and the EEG signal acquisition circuit starts to work; When the slide switch J1 slides to the first pin, the battery power supply circuit is turned off and the battery stops working.
[0041] Based on the above design, it can prevent the current in the circuit and whether the device is working properly when the battery is used for power supply. By using the slide switch J1 to control the power-on, it can prevent the battery from being connected in reverse or incorrectly to affect the circuit. In addition, it can also prevent the circuit from being in a working state when the battery is forgotten to be disconnected, save the battery power to extend the use time, and maintain the battery life.
[0042] In a specific embodiment of the present invention, Figure 6 As shown, the battery charging circuit includes a USB charging interface USB1 and a charging protection chip U13; in the specific implementation process, the USB charging interface is provided with a peripheral circuit for charging, and the peripheral circuit is a prior art, so the present invention will not make too many redundant descriptions; The input end of the USB charging interface USB1 is used for external power supply, and its output end (USB+ pin) is connected to the charging protection chip U13; The charging pin (i.e. Figure 6 The BAT pin of U13 in the circuit is connected to the first pin of the slide switch.
[0043] When the external ambient temperature is greater than the set temperature threshold or the charging power is greater than the set power threshold, the thermal feedback in the charging protection chip adjusts the charging current to reduce the temperature of the charging protection chip. At the same time, the charging protection chip has a battery reverse connection protection function. When the battery is reversely connected, the charging protection chip will shut down and display a fault state, with no charging current. After the reversely connected battery is correctly connected, the charging protection chip automatically starts the charging cycle.
[0044] Since the present invention uses portable batteries for power supply, a battery charging circuit is also designed to charge the battery. The charging interface is a USB port, which can be directly charged by a computer. The circuit stops working, the power is disconnected, and charging is performed. A charging indicator light is also designed: the battery has power, the circuit works normally after power-on, and the green indicator light (LED6) is on; the power is disconnected, the battery is charged, and the red indicator light (LED5) is on. The partial circuit diagram is shown in FIG. Figure 6 shown.
[0045] When the present invention is powered by batteries, a charging protection chip U13 is used to protect the circuit in order to ensure uniform charging of the batteries, avoid imbalance between cells leading to degradation or damage of battery performance, extend the life of the batteries, and ensure battery safety and stable performance.
[0046] like Figure 7 As shown, it is the result of analyzing the collected signal based on the EEG signal acquisition analog front-end circuit of the present invention, (a) represents the original input signal, (b) represents the signal amplitude in the time domain, (c) represents the signal in the frequency domain, and it can be seen from (c) that there is no obvious peak at 50HZ, the 50HZ power frequency can be effectively reduced, and the noise is relatively small.
[0047] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection content of the present invention.
[0048] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.
Claims
1. An electroencephalogram signal acquisition circuit suitable for electroencephalogram signals, characterized in that: Including A / D conversion circuit and electrostatic protection circuit; The A / D conversion circuit includes an A / D conversion chip, a BIAS driving circuit and a routing circuit; The input end of the electrostatic protection circuit is used to connect to the data acquisition electrode of the EEG cap, and the output end thereof is respectively connected to the corresponding N input pins on the A / D conversion chip; The reference pin SRB2 of the A / D conversion chip is used to connect to the reference electrode of the EEG cap, and is also connected to each N input pin of the A / D conversion chip through the routing circuit; The input end of the BIAS driving circuit is connected to the ground electrode of the EEG cap, and the output end thereof is respectively connected to the bias driving output pin, the bias driving input pin and the bias driving in-phase input pin on the A / D conversion chip.
2. The EEG signal acquisition circuit suitable for EEG signals according to claim 1, characterized in that: The BIAS driving circuit includes a first resistor, a second resistor and a first capacitor; One end of the first resistor serves as the input end of the BIAS driving circuit, and the other end thereof is respectively connected to the bias driving output pin and the bias driving input pin on the A / D conversion chip, and is also respectively connected to one end of the second resistor and the first capacitor; The second resistor and the other end of the first capacitor are connected to each other and then connected to the bias drive in-phase input pin on the A / D conversion chip.
3. The EEG signal acquisition circuit suitable for EEG signals according to claim 1, characterized in that: The routing circuit includes a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor and a ninth capacitor; One end of the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, the sixth capacitor, the seventh capacitor, the eighth capacitor and the ninth capacitor is respectively connected to the reference pin SRB2 of the A / D conversion chip, and the other end is respectively connected to the corresponding N input pin on the A / D conversion chip.
4. The EEG signal acquisition circuit suitable for EEG signals according to claim 1, characterized in that: The electrostatic protection circuit includes a first surge protection chip, a second surge protection chip, a third surge protection chip, a fourth surge protection chip, and a fifth surge protection chip which are independent of each other; The four data transmission pins of the first surge protection chip are respectively connected to the P1 pin to the P4 pin of the A / D conversion chip; The four data transmission pins of the second surge protection chip are respectively connected to the P5 pin to the P8 pin of the A / D conversion chip; The four data transmission pins of the third surge protection chip are respectively connected to the input end of the BIAS driving circuit of the A / D conversion chip, and the 6N input pin to the 8N input pin; The four data transmission pins of the fourth surge protection chip are respectively connected to the 2N input pin to the 5N input pin of the A / D conversion chip; The two data transmission pins of the fifth surge protection chip are respectively connected to the 1N input pin and the reference pin of the A / D conversion chip.
5. The EEG signal acquisition circuit suitable for EEG signals according to claim 1, characterized in that: The EEG signal acquisition circuit also includes a voltage stabilizer power supply circuit; the voltage stabilizer power supply circuit includes a voltage stabilizer, a switch, a first linear voltage stabilizer, a second linear voltage stabilizer, a DC-DC power supply conversion chip and a third linear voltage stabilizer; The switch is connected to a voltage stabilizing source; The input end of the first linear regulator is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator and the DC-DC power conversion chip, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip is connected to the input end of the third linear regulator, and the output end of the third linear regulator is connected to the corresponding power supply pin on the A / D conversion chip.
6. The EEG signal acquisition circuit suitable for EEG signals according to claim 5, characterized in that: The first linear regulator receives the 5V voltage output by the switch and outputs a 3.3V digital voltage; The 3.3V digital voltage is sent to the power supply pin of the A / D conversion chip that requires a 3.3V digital voltage, and also serves as the input of the second linear regulator and the DC-DC power conversion chip. When the 3.3V digital voltage is used as the input of the second linear regulator, the second linear regulator outputs a 2.5V analog voltage, and the 2.5V analog voltage is sent to the power supply pin of the A / D conversion chip that requires a 2.5V analog voltage. When the 3.3V digital voltage is used as the input of the DC-DC power conversion chip, the DC-DC power conversion chip outputs an analog -3.3V analog voltage. The -3.3V analog voltage is used as the input of the third linear regulator, and the third linear regulator outputs an analog -2.5V analog voltage, which is sent to the power supply pin of the A / D conversion chip that requires a -2.5V analog voltage.
7. The EEG signal acquisition circuit suitable for EEG signals according to claim 1, characterized in that: The EEG signal acquisition circuit also includes a battery power supply circuit, which includes a battery, a slide switch, a first linear voltage regulator, a second linear voltage regulator, a DC-DC power supply conversion chip and a third linear voltage regulator; The slide switch is connected to a battery; The input end of the first linear regulator is connected to the output end of the switch, and the output end thereof is respectively connected to the input end of the second linear regulator and the DC-DC power conversion chip, and is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the second linear regulator is connected to the corresponding power supply pin on the A / D conversion chip; The output end of the DC-DC power conversion chip is connected to the input end of the third linear regulator, and the output end of the third linear regulator is connected to the corresponding power supply pin on the A / D conversion chip.
8. The electroencephalogram signal acquisition circuit suitable for electroencephalogram signals according to claim 7, characterized in that: The EEG signal acquisition circuit also includes a battery charging circuit, and the output end of the battery charging circuit is connected to the first pin of the sliding switch; The sliding switch comprises a first pin, a second pin and a third pin; When the slide switch slides to the third pin, the battery power supply circuit is powered on, and the EEG signal acquisition circuit starts to work; When the slide switch slides to the first pin, the battery power supply circuit is closed and the battery stops working.
9. The EEG signal acquisition circuit suitable for EEG signals according to claim 8, characterized in that: The battery charging circuit includes a USB charging interface and a charging protection chip; The input end of the USB charging interface is used for external power supply, and the output end is connected to the charging protection chip; The charging pin of the charging protection chip is connected to the first pin of the sliding switch.
10. The EEG signal acquisition circuit suitable for EEG signals according to claim 9, characterized in that: When the external ambient temperature is greater than the set temperature threshold or the charging power is greater than the set power threshold, the thermal feedback in the charging protection chip adjusts the charging current to reduce the temperature of the charging protection chip. At the same time, the charging protection chip has a battery reverse connection protection function. When the battery is reversely connected, the charging protection chip will shut down and display a fault state, with no charging current. After the reversely connected battery is correctly connected, the charging protection chip automatically starts the charging cycle.