Low noise floating current source

Abstract

The application discloses a low-noise floating current source, which comprises a power supply device, a current regulating device and a charging device. The power supply device comprises an energy storage device, which is used for providing electric energy required by the current source. The current regulating device is connected with the power supply device and is used for controlling the power supply device to output current to a load coil according to an external input signal. The charging device comprises a charging power supply and a charging circuit. The charging power supply is connected with the power supply device through the charging circuit. When a current output loop of the current regulating device is connected, the charging circuit is disconnected. When the current output loop of the current regulating device is disconnected, the charging circuit is connected, and the charging power supply is controlled to charge the power supply device. The charging device is connected with the current regulating device and the load coil in parallel. The load coil is used for forming a magnetic field to control atoms. The current output loop comprises the current regulating device and the load coil in series. The current output loop is connected with positive and negative electrodes of the energy storage device. The low-noise floating current source can be provided for cold atom or ultracold atom experiments.

Description

Technical Field

[0001] This invention belongs to the field of current sources, particularly high-precision, low-noise, high-current sources for magnetic field control. Background Technology

[0002] Cold and ultracold atoms provide a highly desirable microscopic quantum state, playing a crucial role in experiments related to quantum physics and quantum information. We need to pass current through coils to generate magnetic fields (magneto-optical traps, magnetic traps) to manipulate the atoms. Because a specific waveform of the magnetic field is required, the current magnitude needs to be simulated and controllable; experiments where atoms are sensitive to magnetic fields also require low noise in the current; experiments need to generate the required magnetic field under a fixed inductance, thus requiring a current of several hundred amperes; some experiments require rapidly increasing the magnetic field, thus placing corresponding requirements on the simulation bandwidth of the circuit and the slew rate of the current.

[0003] Commercially available current sources are typically noisy, bulky, and have slow dynamic response, making them unsuitable for experimental needs. For example, Keysight's 240A power supply 6682A has a current noise level of 40mA (rms, 20Hz to 20MHz) and an output voltage programming time of 45ms.

[0004] High-current sources in the hundreds of amperes range are typically powered by switching power supplies, with current controlled by transistors such as metal-oxide-semiconductor field-effect transistors (MOSFETs). Switching power supplies usually have switching noise, so the current will also contain noise from the switching frequency. Furthermore, although the negative terminal of these switching power supplies may be isolated from the mains ground, capacitive coupling is often present, resulting in poor high-frequency isolation. This can potentially create ground loops, and since many high-power appliances in a laboratory environment generate significant noise from the mains ground, this noise can also couple into the current through the shared ground path.

[0005] Furthermore, cold atom experiments require rapid changes in the magnetic field, thus necessitating a certain bandwidth for the current source. For example, in optical clock experiments, the current needs to be able to switch rapidly (within 2ms) from approximately 30A to a small current of 1.2A.

[0006] In the past, batteries have been used to create small current sources in the mA range, and large batteries have also been used to output DC current. However, currently, there are no batteries used to create such a large current and high bandwidth current source.

[0007] In other words, what urgently needs to be addressed now is to provide a current source with strong noise immunity, the ability to quickly adjust the current magnitude, and high bandwidth. Summary of the Invention

[0008] To improve the noise immunity of the current source, achieve rapid adjustment capability of the current source, and increase the bandwidth of the current source, this disclosure provides a low-noise floating ground current source, the specific scheme of which is as follows.

[0009] A low-noise floating ground current source, comprising:

[0010] A power supply device, wherein the power supply device includes an energy storage device for providing the electrical energy required by the low-noise floating ground current source;

[0011] A current regulating device, connected to the power supply device, is used to control the power supply device to output current to the load coil according to an external input signal;

[0012] A charging device includes a charging power supply and a charging circuit. The charging power supply is connected to the power supply device through the charging circuit. When the current output circuit of the current regulating device is connected, the charging circuit is disconnected. When the current output circuit of the current regulating device is disconnected, the charging circuit is connected to control the charging power supply to charge the power supply device. The charging device is connected in parallel with the current regulating device and the load coil. The load coil is used to form a magnetic field to control atoms after being connected in series with the current regulating device. The current output circuit includes the current regulating device and the load coil connected in series. The two ends of the current output circuit are connected to the positive and negative electrodes of the energy storage device.

[0013] According to some embodiments provided in this disclosure, the current regulating device includes an adjusting tube and an adjusting tube driving circuit, the adjusting tube being connected in series with the load coil, and the adjusting tube including an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

[0014] According to some embodiments provided in this disclosure, the current regulating device further includes a current sensor and a computing device. The current sensor is connected in series with the regulating tube and is used to detect the current in the current output circuit. The computing device performs calculations on the current detected by the current sensor. The regulating tube driving circuit controls the regulating tube to change the current in the current output circuit according to the result of the calculation. The result of the calculation includes the error between the current detected by the current sensor and the external input control signal.

[0015] According to some embodiments provided in this disclosure, the current sensor includes a fluxgate current sensor.

[0016] According to some embodiments provided in this disclosure, the computing device uses a proportional-integral-differential algorithm for calculation.

[0017] According to some embodiments provided in this disclosure, when the computing device performs calculations using a proportional-integral-derivative algorithm, dynamic gain control technology is used to keep the gain of the adjustment transistor drive circuit constant. The computing device adjusts the weight of the proportional-integral-derivative operation of the transconductance of the adjustment transistor according to the current magnitude detected by the current sensor, thereby controlling the magnitude of the gain of the adjustment transistor drive circuit.

[0018] According to some embodiments provided in this disclosure, the dynamic gain control technology includes feedforward technology or feedback technology, and the dynamic gain control technology employs digital circuits or analog circuits.

[0019] According to some embodiments provided in this disclosure, when the computing device uses analog circuits, the control signal x is processed by taking the square root of the analog circuit after proportional-integral-differential operations to achieve a power reduction effect. The formula for taking the square root of the analog circuit includes: Where a1, b1, and c1 are system parameters.

[0020] According to some embodiments provided in this disclosure, when the computing device employs digital circuits and digital feedforward technology, the control signal x is subjected to square root processing in an FPGA (Field Programmable Gate Array) after proportional-integral-differential operations. The formula for square root processing via digital circuits includes: Where a2, b2, and c2 are system parameters.

[0021] According to some embodiments provided in this disclosure, when the computing device employs digital circuitry and digital feedback technology, the system response function G(ω,I) is obtained through measurement. p ), calculate the control law K(ω,I) P This makes the system closed-loop response T = 1 + iω / ω', and the formula for calculating the control rule is:

[0022]

[0023]

[0024] G(ω,I p K(ω,I) is the system response function, which is obtained through testing and approximated using a second-order system simulation. P ) represents the control law, ω represents the angular frequency, ω1 and ω2 are the first-order and second-order angular frequency parameters related to the output current in the system response function, respectively, ω' is the corner frequency of the first-order system formed by closed-loop feedback, and i is the imaginary unit. p Let T(ω) be the output current, and T(ω) be the closed-loop response function of the entire system.

[0025] According to some embodiments provided in this disclosure, the regulating tube drive circuit uses a pre-pulse to adjust the current in the regulating tube, and sets an overshoot control on the falling edge of the input voltage to control the falling edge of the output current. When the current needs to be reduced, the voltage is first reduced to the minimum value of the rated voltage, and then the voltage is gradually increased to the voltage required for the target current value; when the current needs to be increased, the voltage is first increased to the maximum value of the rated voltage, and then the voltage is gradually reduced to the voltage required for the target current value.

[0026] According to some embodiments provided in this disclosure, an optocoupler is provided between the computing device and the adjustment tube drive circuit to reduce interference between the computing device and the current output circuit.

[0027] The above technical solutions reduce the interference of mains power to the load circuit by using energy storage devices as power supply devices, and prevent interference introduced by the charging power supply by using charging devices to charge at the output intervals of the power supply devices. Attached Figure Description

[0028] Figure 1 A schematic block diagram illustrating the structure of a low-noise floating ground current source according to an embodiment of the present disclosure is shown.

[0029] Figure 2 A schematic diagram illustrating the pre-pulse effect of a low-noise floating ground current source according to an embodiment of the present disclosure is shown.

[0030] Figure 3 The schematic diagram illustrates a low-noise floating ground current source PI control circuit using an analog circuit according to an embodiment of the present disclosure.

[0031] Figure 4 The schematic diagram illustrates a digital circuit for the PI control circuit of a low-noise floating ground current source according to an embodiment of the present disclosure.

[0032] Figure 5 The schematic diagram illustrates an analog circuit of a low-noise floating ground current source employing dynamic gain control technology according to an embodiment of the present disclosure.

[0033] Figure 6 A schematic block diagram of a low-noise floating ground current source structure according to another embodiment of the present disclosure is shown. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0035] However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0036] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0037] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way. For example, a PID controller refers to proportional-integral-derivative (PID) control; a farad capacitor, also called a double-layer capacitor, gold capacitor, or supercapacitor, is a chemical component developed in the 1970s and 80s; and an FPGA (Field Programmable Gate Array) is a further development based on programmable devices such as PAL and GAL, emerging as a semi-custom circuit in the field of application-specific integrated circuits (ASICs), addressing the shortcomings of custom circuits while overcoming the limited gate count of traditional programmable devices.

[0038] A low-noise floating ground current source includes a power supply device, a current regulation device, and a charging device.

[0039] According to some embodiments provided in this disclosure, the power supply device includes an energy storage device for providing the electrical energy required by a low-noise floating ground current source.

[0040] According to some embodiments provided in this disclosure, the energy storage device includes a battery, a supercapacitor, or other energy storage devices. Based on the low noise of the battery and supercapacitor themselves, the noise of their output current can also be very low.

[0041] According to some embodiments provided in this disclosure, in some experiments involving cold or ultracold atoms, experiments where atoms are sensitive to magnetic fields require relatively low noise in the circuit. Conventional mains power supply or conventional switching power supply cannot meet the experimental requirements. In addition, general commercial current sources are noisy, bulky, and have slow dynamic response, which cannot meet the experimental needs.

[0042] According to some embodiments provided in this disclosure, using a battery or a supercapacitor as an energy storage device can avoid the switching noise that is typically encountered when using a switching power supply.

[0043] According to some embodiments provided in this disclosure, this disclosure utilizes the floating ground characteristics of a battery or supercapacitor, where the negative terminal is isolated from the mains ground or earth ground, which can effectively isolate it from the mains power and will not form a ground loop, thus avoiding noise interference from other devices to the load in the circuit of the current source of this disclosure.

[0044] According to some embodiments provided in this disclosure, the current regulating device is connected to the power supply device and is used to control the power supply device to output current to the load coil according to an external input signal.

[0045] According to some embodiments provided in this disclosure, in some experiments involving cold atoms or ultracold atoms, it is necessary to pass current through a coil to generate a magnetic field (such as a magneto-optical trap, magnetic trap, etc.) to manipulate the atoms. Generating the magnetic field with the aforementioned specific waveform requires precise control of the current magnitude. In this disclosure, a current regulating device is used to control the magnitude of the current in the load current.

[0046] According to some embodiments provided in this disclosure, the charging device includes a charging power supply and a charging circuit, wherein the charging power supply is connected to the power supply device through the charging circuit.

[0047] According to some embodiments provided in this disclosure, the charging circuit is disconnected when the current output circuit of the current regulating device is connected.

[0048] According to some embodiments provided in this disclosure, when the current output circuit of the current regulating device is disconnected, the charging circuit connects to control the charging power supply to charge the power supply device.

[0049] The charging device is connected in parallel with the current regulating device and the load coil. The load coil is used to form a magnetic field to control the atoms after being connected in series with the current regulating device. The current output circuit includes the current regulating device and the load coil connected in series. The two ends of the current output circuit are connected to the positive and negative electrodes of the energy storage device.

[0050] According to some embodiments provided in this disclosure, the voltage of the battery or supercapacitor will gradually decrease as it discharges. In some cold atom or ultracold atom experiments, the current or high current is not continuously output. Generally, in an experimental cycle, there may be 1 / 10 of the time that a high current output is required, while the other time is used for other experimental steps. Therefore, the battery or supercapacitor can be charged during the experimental interval.

[0051] According to some embodiments provided in this disclosure, if the ground of the charging power supply and the current source system are connected, noise will also be introduced into the circuitry for cold atoms or ultracold atoms. Therefore, as Figure 1As shown, two relays are configured to control the connection between the positive and negative terminals of the battery or supercapacitor and the charging device, respectively. The two relays are only activated when the battery or supercapacitor is charging; at other times, they are deactivated to prevent the charging device from affecting the battery or supercapacitor. Specifically, the activation and deactivation of the two relays are controlled by a charging control signal.

[0052] By replacing conventional switching power supplies with batteries or supercapacitors, the switching noise introduced into the current by switching power supplies is eliminated. Simultaneously, the negative terminal of the battery or supercapacitor is isolated from the mains ground or earth ground, thus achieving electrical isolation from the mains power and eliminating potential ground loops. This prevents interference from other instruments and equipment in the laboratory with the output current, achieving extremely low current noise at high currents in the hundreds of amperes range, with a relative stability of 10%. -5 This current source can be used for noise-critical experiments such as the preparation of two-dimensional quantum gases.

[0053] According to some embodiments provided in this disclosure, the current regulating device includes an adjusting tube and an adjusting tube driving circuit, wherein the adjusting tube is connected in series with the load coil.

[0054] According to some embodiments provided in this disclosure, the regulating transistor includes an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

[0055] According to some embodiments provided in this disclosure, the current regulating device further includes a current sensor and a computing device.

[0056] According to some embodiments provided in this disclosure, a current sensor is connected in series with a regulating tube to detect the current in the current output circuit.

[0057] According to some embodiments provided in this disclosure, the computing device performs calculations on the current detected by the current sensor, and the adjustment tube drive circuit controls the adjustment tube to change the current in the current output circuit according to the calculation result.

[0058] According to some embodiments provided in this disclosure, the result of the calculation includes the error between the current detected by the current sensor and the external input control signal.

[0059] like Figure 1 As shown, according to some embodiments provided in this disclosure, the current sensor sends the detected current signal to a PI (proportional-integral) control unit. The PI control unit performs PI calculations based on the received analog / digital control signal and the received current signal, and outputs a control signal. The control signal output by the PI control unit controls the driving power of the regulating transistor through optocoupler isolation, adjusting the voltage across the regulating transistor and thus changing the current within the regulating transistor. The feedback circuit of the current sensor is grounded through a sampling resistor to prevent the formation of a ground loop, which could lead to interference from other devices.

[0060] The load coil includes a coil, a gas discharge tube and a varistor connected in parallel with the coil. When the load coil receives a current of a specific waveform, it forms a corresponding magnetic field and completes the control of the atoms in the magnetic field.

[0061] According to some embodiments provided in this disclosure, such as Figure 6 As shown, PI control can be directly connected to the regulating transistor circuit. Since its battery is a floating power supply, a single-point grounding at the control terminal does not introduce a ground loop.

[0062] According to some embodiments provided in this disclosure, in order to reduce noise and long drift affecting the output current, the current sensor in this disclosure includes a fluxgate current sensor.

[0063] According to some embodiments provided in this disclosure, when an invariant gain exists in the circuit, the loop gain of different current systems is different, and some currents will oscillate, such as... Figure 5 As shown, this disclosure employs dynamic gain control technology in the regulating transistor circuit, performing square root processing on the control signal x after PI calculation, i.e., sqrt(ax+b)+c, where a, b, and c are system parameters. When the output current is small, the gain of the feedback loop is increased, so that the feedback loop gain tends to remain constant under different output currents, thus solving the problem that the output current cannot keep up with the input signal when the current is small.

[0064] According to some embodiments provided in this disclosure, the computing device uses a PID controller for calculation.

[0065] According to some embodiments provided in this disclosure, the PID controller performs calculations including an analog PI operation section or a digital PI processor, converts the feedback signal into a digital signal using an ADC, performs PI operations on the feedback signal using an FPGA or a microcontroller-like device, and then converts the calculated result into an analog control voltage using a DAC.

[0066] According to some embodiments provided in this disclosure, during digital PI operation, the weight of the PI operation can be adjusted according to the measured transconductance (system function) to realize dynamic gain control technology, thereby achieving the effect of keeping the feedback loop gain constant when the gate voltage value is different.

[0067] According to some embodiments provided in this disclosure, when using a PID controller, dynamic gain control technology is employed to keep the gain of the regulating transistor drive circuit constant.

[0068] According to some embodiments provided in this disclosure, the computing device adjusts the weight of the transconductance regulation ratio-integral-derivative operation of the regulating transistor based on the magnitude of the current detected by the current sensor, thereby controlling the gain of the regulating transistor drive circuit.

[0069] According to some embodiments provided in this disclosure, dynamic gain control technology includes feedforward technology or feedback technology, and dynamic gain control technology employs digital circuits or analog circuits.

[0070] According to some embodiments provided in this disclosure, such as Figure 3 As shown, the PI control includes an operational amplifier (ADA4522), a first sliding rheostat, a capacitor, and a second sliding rheostat. The positive input terminal of the operational amplifier receives the control signal, and the negative input terminal receives the signal fed back from the current sensor. The output terminal of the operational amplifier is connected to the adjustment transistor drive circuit. One end of the capacitor is connected to the negative input terminal of the operational amplifier, and the other end is connected to one end of the first sliding rheostat. The other end of the first sliding rheostat is connected to the output terminal of the operational amplifier. One end of the second sliding rheostat is connected to the negative input terminal of the operational amplifier, and the other end is connected to the current sensor. The PI control performs PI calculations based on the feedback signal and the input analog control signal, outputs a control signal, and then changes the voltage across the adjustment transistor through the adjustment transistor drive circuit to control the current inside the adjustment transistor.

[0071] When the computing device uses analog circuits, the control signal x is processed by the PID controller and then subjected to square root operation through the analog circuit to achieve a power reduction effect, making the system response closer to linear.

[0072] According to some embodiments provided in this disclosure, such as Figure 4 As shown, the PI operation control includes an FPGA, an analog-to-digital converter (ADC), and a digital-to-analog converter (DAC). The signal fed back by the current sensor is converted by the ADC and then sent to the FPGA. The FPGA performs PI operation on the feedback signal converted by the ADC according to the received digital control signal, and sends the operation result to the DAC to be converted into a control signal (analog control voltage) and then output. The regulating tube drive circuit adjusts the current in the regulating tube according to the control signal output by the DAC.

[0073] in, Figure 3 and Figure 4 The PI control section can be an analog PI amplifier consisting of a precision operational amplifier such as OP177 or ADA4522 and resistors and capacitors; or it can be a digital PI processor that converts the feedback signal into a digital signal using an ADC, performs PI calculations on the feedback signal using an FPGA or microcontroller, and then converts the calculated result into an analog control voltage using a DAC. The PI control section uses a linear power supply or battery to reduce noise in the output current.

[0074] According to some embodiments provided in this disclosure, the arithmetic device performs square root operations using analog circuits, including: Where a1, b1, and c1 are system parameters. The response of the regulating tube is approximately a high-order function. a1, b1, and c1 were obtained through testing and debugging. The setting principle is to make... The product of the transfer function of the regulating tube and the transfer function of the regulating tube tends to be linear, so as to compensate for the problem that the transfer function (AC transconductance) of the regulating tube is too small when the current is low.

[0075] According to some embodiments provided in this disclosure, when the computing device employs digital circuits and digital feedforward technology, the control signal x is processed by the PID controller and then subjected to square root operations in the FPGA to achieve a power reduction effect, making the system response closer to linear. This control algorithm can be implemented in an FPGA, a CPLD (Complex Programmable Logic Device), or a microcontroller.

[0076] According to some embodiments provided in this disclosure, the arithmetic device performs square root operations using digital circuits, including: Where a2, b2, and c2 are system parameters. The response of the regulating tube is approximately a high-order function. a1, b1, and c1 were obtained through testing and debugging. The setting principle is to make... The product of the transfer function of the regulating tube and the transfer function of the regulating tube tends to be linear, so as to compensate for the problem that the transfer function (AC transconductance) of the regulating tube is too small when the current is low.

[0077] According to some embodiments provided in this disclosure, when the computing device employs digital circuitry and digital feedback technology, the system response function G(ω,I) is obtained through measurement. p ), calculate the control law K(ω,I) P This makes the system closed-loop response T = 1 + iω / ω', and the formula for calculating the control rule is:

[0078]

[0079]

[0080] Where G(ω,I) p K(ω,I) is the system response function, which is obtained through testing and approximated using a second-order system simulation. P ) represents the control law, ω represents the angular frequency, ω1 and ω2 are the first-order and second-order angular frequency parameters related to the output current in the system response function, respectively, ω' is the corner frequency of the first-order system formed by closed-loop feedback, and i is the imaginary unit. p Let T(ω) be the output current, and T(ω) be the closed-loop response function of the entire system.

[0081] According to some embodiments provided in this disclosure, in some cold atom and ultracold atom experiments, it is necessary to rapidly increase the magnetic field, thus placing high demands on the analog bandwidth of the circuit and the slew rate of the current.

[0082] According to some embodiments provided in this disclosure, the conventional method of changing the current and gradually changing the voltage results in a very slow change in current response to voltage due to insufficient transconductance when the current of the regulating tube is close to 0.

[0083] According to some embodiments provided in this disclosure, such as Figure 2 As shown by the solid line, when the current switches from 30A to 1.2A, the transconductance decreases as the current decreases. Approaching 1.2A, the current-voltage response changes very slowly, as... Figure 2 As shown by the solid line, the current curve will have a very long "tail".

[0084] According to some embodiments provided in this disclosure, the adjustment tube drive circuit uses a pre-pulse to adjust and change the current in the adjustment tube.

[0085] According to some embodiments provided in this disclosure, an overshoot control is set by setting the falling edge of the input voltage to control the falling edge of the output current. The intensity and duration of the overshoot are adjusted to minimize the falling edge of the output current pulse. When the current needs to be reduced, the voltage is first reduced to the minimum value of the rated voltage, and then the voltage is gradually increased to the voltage required for the target current value. For example, as... Figure 2 As shown, the input voltage is first reduced to a negative voltage, and then gradually increased to the voltage required for a 1.2A current. The waveform is as follows. Figure 2 As shown by the dashed line, this waveform adjustment method is called a prepulse.

[0086] According to some embodiments provided in this disclosure, such as Figure 2 As shown, the current switches from 30A to 1.2A and stabilizes in less than 400µs, which meets the requirements of optical clock experiments.

[0087] According to some embodiments provided in this disclosure, the adjustment of the prepulse waveform needs to be based on the actual load calculation and the actual system conditions such as the response of the regulating tube, and then the waveform parameters need to be adjusted to complete the adjustment of the prepulse waveform.

[0088] According to some embodiments provided in this disclosure, when the current needs to be increased, the voltage is first increased to the maximum value of the rated voltage, and then the voltage is gradually reduced to the voltage required for the target current value.

[0089] According to some embodiments provided in this disclosure, an optocoupler is provided between the computing device and the regulating transistor drive circuit to reduce interference from the computing device to the current output circuit.

[0090] By employing the above technical solution, replacing conventional switching power supplies with batteries or supercapacitors, the switching noise introduced into the current by switching power supplies is eliminated. Simultaneously, the negative terminal of the battery or supercapacitor is isolated from the mains ground or earth ground, thus achieving electrical isolation from the mains power and eliminating potential ground loops. This prevents interference from other instruments and equipment in the laboratory with the output current, achieving extremely low current noise at high currents in the hundreds of amperes range, with a relative stability of 10%. -5 This current source can be used in noise-critical experiments such as the preparation of two-dimensional quantum gases; it has low output current drift and a high bandwidth of the current regulation system, solving the technical problem of slow current response to voltage changes. At the same time, it can also eliminate current oscillations caused by different loop gains in different current systems.

[0091] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. Furthermore, the definitions of the various components described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0092] It should also be noted that, in the specific embodiments of this disclosure, unless otherwise stated otherwise, the numerical parameters in this specification and the appended claims are approximate values ​​and can be changed according to the desired characteristics obtained from the content of this disclosure. Specifically, all numbers used in the specification and claims to indicate dimensions, range conditions, etc., of the composition should be understood to be modified by the term "about" in all cases. Generally, this means that there may be variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0093] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-noise floating ground current source, characterized in that, include: A power supply device, wherein the power supply device includes an energy storage device for providing the electrical energy required by the low-noise floating ground current source, the energy storage device including one of the following: a battery, a supercapacitor, and the negative terminal of the battery or the supercapacitor is isolated from the mains ground or the earth ground; A current regulating device, connected to the power supply device, is used to control the power supply device to output current to the load coil according to an external input signal; A charging device includes a charging power supply and a charging circuit. The charging power supply is connected to the power supply device through the charging circuit. When the current output circuit of the current regulating device is connected, the charging circuit is disconnected; when the current output circuit of the current regulating device is disconnected, the charging circuit is connected to control the charging power supply to charge the power supply device. Two relays are configured to control the connection of the positive and negative terminals of the battery or the supercapacitor to the charging device, respectively. The charging device is connected in parallel with the current regulating device and the load coil. The load coil, after being connected in series with the current regulating device, is used to form a magnetic field to control atoms. The current output circuit includes the current coil connected in series. The current output circuit is connected to the positive and negative electrodes of the energy storage device. The current regulating device includes an adjusting tube, an adjusting tube drive circuit, a current sensor, and a computing device. The computing device uses a proportional-integral-differential algorithm for calculation. When performing the proportional-integral-differential algorithm, the computing device uses dynamic gain control technology to keep the gain of the adjusting tube drive circuit constant. The computing device adjusts the transconductance of the adjusting tube according to the current detected by the current sensor to adjust the weight of the proportional-integral-differential operation, thereby controlling the gain of the adjusting tube drive circuit. The dynamic gain control technology uses digital circuits or analog circuits. When using analog circuits, the arithmetic device performs proportional-integral-differential operations and then performs square root operations on the control signal x through the analog circuit to achieve a power reduction effect. The formula for performing square root operations through the analog circuit includes: Where a1, b1, and c1 are system parameters; When digital circuits and digital feedforward technology are used, the computing device performs square root operations on the control signal x in a field-programmable gate array after proportional-integral-differential operations. The formula for square root operations using digital circuits includes: , where a2, b2, and c2 are system parameters.

2. The low-noise floating ground current source according to claim 1, characterized in that, The regulating transistor is connected in series with the load coil, and the regulating transistor includes an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

3. The low-noise floating ground current source according to claim 2, characterized in that, The current sensor is connected in series with the regulating tube to detect the current in the current output circuit. The computing device performs calculations on the current detected by the current sensor. The regulating tube driving circuit controls the regulating tube to change the current in the current output circuit according to the result of the calculation. The result of the calculation includes the error between the current detected by the current sensor and the external input control signal.

4. The low-noise floating ground current source according to claim 3, characterized in that, The current sensor includes a fluxgate current sensor.

5. The low-noise floating ground current source according to claim 1, characterized in that, The dynamic gain control technology includes feedforward technology or feedback technology.

6. The low-noise floating ground current source according to claim 1, characterized in that, When digital circuits and digital feedback technology are used, the computing device obtains the system response function G(ω,I) through measurement. p The system described here includes the regulating transistor drive circuit, the regulating transistor, and the current sensor, and the control law K(ω,I) is calculated in the digital controller. P This makes the desired closed-loop response of the entire system T = 1 + iω / ω', and the calculation formula of the control law is as follows: include: （1） （2） Where G(ω,I) p K(ω,I) is the system response function, which is obtained through testing and approximated using a second-order system simulation. P ) represents the control law, and ω represents the angular frequency. , These are the first-order and second-order angular frequency parameters related to the output current in the system response function, used for approximation; ω' is the corner frequency of the first-order system formed by closed-loop feedback; i is the imaginary unit; and I... p For output current, This is the response function of the entire system after the loop is closed.

7. The low-noise floating ground current source according to claim 2, characterized in that, The regulating tube drive circuit uses a pre-pulse to adjust and change the current in the regulating tube. An overshoot control is set by the falling edge of the input voltage to control the falling edge of the output current. When the current needs to be reduced, the voltage is first reduced to the minimum value of the rated voltage, and then the voltage is gradually increased to the voltage required for the target current value. When the current needs to be increased, first raise the voltage to the maximum value of the rated voltage, and then gradually reduce the voltage to the voltage required for the target current value.

8. The low-noise floating ground current source according to any one of claims 1 to 6, characterized in that, An optocoupler is provided between the computing device and the adjustment tube drive circuit to reduce interference between the computing device and the current output circuit.

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