A constant current control circuit capable of outputting multi-waveform electrical stimulation

Abstract

The utility model provides a kind of constant current control circuit that can output multiple waveform electric stimulation, including single-chip microcontroller control module, for generating two-way complementary PWM drive signal, constant current control signal and receiving feedback signal;Full-bridge inverter circuit, it is made of four switching devices, its input end receives the two-way complementary PWM drive signal;Constant current control circuit, for sampling output current and generating current feedback signal transmission to the single-chip microcontroller control module;Output voltage detection circuit, for sampling output voltage and generating voltage feedback signal transmission to the single-chip microcontroller control module;Wherein, the single-chip microcontroller control module is adjusted according to the current feedback signal and voltage feedback signal, and its output drive signal is adjusted, and constitutes closed loop control.The utility model simplifies drive control circuit, improves the precision of output voltage and current, realizes stable electric stimulation output, simultaneously meets the output waveform demand of different types, to adapt to various complex application scenarios.

Description

Technical Field

[0001] This utility model relates to the fields of medical rehabilitation and electrical stimulation technology, specifically to a constant current control circuit capable of outputting multi-waveform electrical stimulation. Background Technology

[0002] Electrical stimulation therapy is a widely used physical therapy method in medical rehabilitation, muscle training, and relieving muscle pain. Its basic principle is to stimulate nerve or muscle tissue with electrical current, utilizing electrophysiological principles to achieve therapeutic effects. Currently, electrical stimulation output solutions mainly include transformer boost output, half-bridge inverter output, and full-bridge inverter output.

[0003] While transformer-based step-up outputs control the output voltage and current by manipulating the input voltage and current on the primary side of the transformer, their reliance on the linear output characteristic of transformers limits their controllability. Furthermore, with the increasing sophistication of clinical applications, the demands for diverse output waveforms are becoming more complex, making it difficult to meet these requirements solely through transformer-based step-up outputs. While half-bridge output circuits are structurally simple, they require a large number of switches, and their output voltage is only half that of the DC bus voltage. Full-bridge output circuits, although capable of achieving higher output voltages, require four switching devices, have complex drive logic, are more expensive, and necessitate precise calculation of dead time to prevent shoot-through between the upper and lower bridge arms.

[0004] There are currently some patent documents addressing the problems of complex driving logic and low output accuracy in electrical stimulation output devices.

[0005] For example, CN111725977A discloses an electrical stimulation circuit, which includes a waveform control circuit, a conduction control circuit, an H-bridge circuit, and an isolation transformer. The waveform control circuit outputs an electrical stimulation signal of a corresponding waveform to the H-bridge circuit based on a waveform control signal. The conduction control circuit controls the conduction state of each transistor in the H-bridge circuit, causing the H-bridge circuit to output an electrical stimulation signal to the primary winding of the isolation transformer. However, this electrical stimulation circuit relies on analog circuitry for waveform generation, resulting in insufficient accuracy and flexibility; the H-bridge driving logic is complex, requiring multiple control signals; furthermore, it lacks a closed-loop constant current control mechanism, leading to poor output stability.

[0006] CN102711906B discloses an electrical stimulation device, which includes a transformerless boost circuit, a first electrode and a second electrode, an amplifier circuit, a controller, an H-bridge circuit, an insulated DC-DC converter, a regulator, and a third electrode. The device is controlled by the controller via the H-bridge circuit to output a stimulation signal. However, this device lacks an effective constant current control mechanism, resulting in poor output current stability; its waveform generation capability is limited, making it difficult to achieve complex therapeutic waveforms; furthermore, the circuit structure is complex, requiring multiple switches and isolation modules, leading to low integration.

[0007] Therefore, there is an urgent need for a constant current control circuit that can output multi-waveform electrical stimulation, which can simplify the drive control circuit, reduce the complexity of the drive logic, improve the accuracy of the output voltage and current, and achieve stable and reliable electrical stimulation output to meet the requirements of different types of output waveforms and adapt to various complex application scenarios. Utility Model Content

[0008] In view of the problems that existing technologies have, such as complex driving logic, low output accuracy, large size and high cost of electrical stimulation output devices, this utility model provides a constant current control circuit that can output multi-waveform electrical stimulation in order to solve the above problems.

[0009] To achieve the above objectives, this utility model provides the following technical solution: a constant current control circuit capable of outputting multi-waveform electrical stimulation, comprising: The microcontroller control module is used to generate two complementary PWM drive signals, a constant current control signal, and to receive feedback signals. The full-bridge inverter circuit consists of four switching devices. Its input terminal receives the two complementary PWM drive signals. Each drive signal synchronously controls a set of diagonal switching devices in the full-bridge inverter circuit to invert the DC bus voltage into an AC stimulation waveform. A constant current control circuit, whose input terminal is connected in series with the output circuit of the full-bridge inverter circuit, is used to sample the output current and generate a current feedback signal to be sent to the microcontroller control module. An output voltage detection circuit, whose input terminal is connected in parallel with the output terminal of the full-bridge inverter circuit, is used to sample the output voltage and generate a voltage feedback signal to be sent to the microcontroller control module. The microcontroller control module adjusts its output drive signal based on the current feedback signal and voltage feedback signal, and forms a closed-loop control to achieve constant current control and waveform output.

[0010] Compared with the prior art, the beneficial effects of this utility model are as follows: The full-bridge inverter output circuit is adopted, and the drive signal is issued through the microcontroller control module. The full-bridge circuit is driven by two complementary drive signals, which significantly simplifies the drive control circuit, reduces the complexity of the drive logic, and solves the problems of complex drive logic and high cost of traditional full-bridge output circuits. By adopting a closed-loop control method, the microcontroller can adjust the drive signal in real time according to the detected voltage and current signals, making the output voltage and current more stable and improving the reliability and adaptability of the system. In addition, the control circuit can realize a variety of waveform outputs to meet different types of electrical stimulation needs, and there is no need for a transformer step-up stage, avoiding the limitations caused by the excessive size of the transformer, making it suitable for miniaturized and portable devices. Attached Figure Description

[0011] The disclosure of this utility model is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this utility model. In the drawings, the same reference numerals are used to refer to the same parts. Wherein: Figure 1 This is a block diagram of the constant current control circuit proposed in the embodiments of this utility model. Detailed Implementation

[0012] It is readily understood that, based on the technical solution of this utility model, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of this utility model. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative descriptions of the technical solution of this utility model and should not be considered as the entirety of this utility model or as limitations or restrictions on the technical solution of this utility model.

[0013] The present invention will be further described in detail below with reference to the accompanying drawings, but this is not intended to limit the present invention.

[0014] like Figure 1 As shown, this utility model proposes a constant current control circuit capable of outputting multi-waveform electrical stimulation. The control circuit adopts a full-bridge inverter output circuit, and sends a drive signal through a microcontroller control module. It uses two complementary drive signals to drive the full-bridge circuit, effectively solving the problem of logic complexity and high cost caused by the traditional full-bridge circuit requiring four drive signals, thereby simplifying the drive control and reducing the logic complexity.

[0015] Specifically, the constant current control circuit includes a microcontroller control module, a full-bridge inverter circuit, a constant current control circuit, a current detection circuit, and an output voltage detection circuit. The microcontroller control module generates drive signals and constant current control signals, and receives feedback signals from current detection and output voltage detection. Its output generates two complementary PWM signals, which drive the full-bridge inverter circuit via the bridge arm drive circuit, and simultaneously outputs a PWM-PWR control signal to the voltage regulation module. Its input connects to the feedback signals from the current detection circuit and the output voltage detection circuit, forming a closed-loop control. The full-bridge inverter circuit includes four switching devices, controlled by two complementary drive signals to achieve full-bridge circuit driving, avoiding the problem of traditional full-bridge circuits requiring four drive signals.

[0016] To achieve precise current output and avoid current fluctuations caused by load changes, a symmetrical constant current control circuit and a current detection circuit are incorporated into the full-bridge inverter circuit. The constant current control circuit includes a precision sampling resistor and an operational amplifier. The precision sampling resistor is connected in series in the output circuit, and the sampled voltage across it is sent to a differential amplifier composed of operational amplifiers for amplification. The amplified voltage signal is then output as a current feedback signal to the ADC sampling pin of the microcontroller control module. This differential amplification structure effectively suppresses common-mode interference and improves current sampling accuracy. The microcontroller control module generates a corresponding constant current control signal based on the current detection signal and the preset constant current value, thereby achieving constant current control of the full-bridge circuit through the constant current control circuit.

[0017] To further enhance system safety and prevent overcurrent damage to circuits or user discomfort, an independent current detection circuit is provided. This current detection circuit consists of a current sensor and a comparator. It acquires the current signal through the precision sampling resistor and converts it into a voltage signal. The comparator compares the voltage signal with a reference voltage and outputs a current detection signal to the microcontroller control module. Specifically, the current detection circuit can share the same sampling resistor with the constant current control circuit, which not only saves components but also ensures that the current signal sources used for control and protection are consistent, improving system consistency. The non-inverting input of the comparator is connected to the sampled voltage signal, the inverting input is connected to the set reference voltage, and its output is connected to the I / O port of the microcontroller control module for rapid fault indication.

[0018] Furthermore, to achieve precise management of the output voltage and provide overvoltage protection, the output voltage detection circuit includes a voltage divider resistor and an operational amplifier. This circuit acquires the output voltage of the full-bridge inverter circuit and feeds it back to the microcontroller control module. The circuit consists of a resistor divider formed by two high-precision resistors connected in series, directly connected in parallel to the output of the full-bridge inverter circuit. The midpoint of the voltage divider is connected to a voltage follower formed by the operational amplifier for impedance matching. The application of the voltage follower ensures the stability of the sampling point voltage, avoiding the load effect of the subsequent ADC sampling circuit on the resistor divider, thus ensuring the accuracy of the voltage measurement. The output of the voltage follower is connected to another ADC sampling pin of the microcontroller control module. Based on the output voltage detection signal and the preset output voltage value, the microcontroller control module adjusts the duty cycle of the drive signal to achieve precise control of the output voltage.

[0019] The microcontroller control module also includes a waveform control unit, used to generate control signals for various waveforms. Specifically, the waveform control unit uses a digital signal processor (DSP) chip and employs software algorithms to generate various waveforms, including square waves, triangle waves, trapezoidal waves, sine waves, and more. The waveform control unit also features programmable frequency and duty cycle settings, allowing for flexible configuration of output parameters according to different treatment needs.

[0020] The full-bridge inverter circuit uses four MOSFETs as its switching devices, forming a full-bridge structure. It is controlled by two complementary drive signals received from the bridge arm drive circuit: one drive signal controls the upper left and lower right bridge arm circuits, and the other drive signal controls the upper right and lower left bridge arm circuits. Specifically, the four MOSFETs (Q1, Q2, Q3, Q4) are connected as follows: the drains of Q1 and Q3 are connected to the DC bus voltage output by the voltage regulation module; the source of Q1 is connected to the drain of Q2, forming the first output terminal; the source of Q3 is connected to the drain of Q4, forming the second output terminal; the sources of Q2 and Q4 are grounded together. The first PWM drive signal output by the microcontroller control module simultaneously controls the gates of Q1 and Q4 via the drive circuit, and the second PWM drive signal simultaneously controls the gates of Q2 and Q3 via the drive circuit. The addition of two drive signals with a 60° phase shift, through a preset fixed phase difference, provides the necessary dead time for the switching transistor's turn-off and turn-on, effectively avoiding the risk of shoot-through between the upper and lower bridge arms and greatly improving system reliability. The drive signals are generated using PWM signals, implemented through the PWM output port of the microcontroller control module.

[0021] To adapt to the dynamic demands of electrical stimulation therapy on output voltage amplitude and improve energy efficiency, the control circuit also includes a voltage regulation module. This module can boost the low voltage provided by the DC power supply module to the high voltage level required for electrical stimulation. Its input terminal connects to the DC power supply module, and its enable or control terminal receives a PWM-PWR signal from the microcontroller. By changing the duty cycle of this PWM-PWR signal, the microcontroller can precisely and continuously adjust the output voltage of the module, which directly serves as the DC bus voltage of the full-bridge inverter circuit. Based on the voltage regulation module, the system can start from a relatively low input voltage, directly generate and precisely control the high voltage applied to the full-bridge circuit, while ensuring excellent energy conversion efficiency. The voltage regulation module is composed of integrated circuit chips (ICs) and peripheral components, and integrates overvoltage protection and maximum output current protection functions to ensure the safe and reliable operation of the circuit.

[0022] To achieve self-monitoring and protection of the control circuit, a fault protection module is installed at the input of the control circuit to detect the output status of the full-bridge inverter circuit. The fault protection module includes current and voltage sensors for real-time monitoring of the output current and voltage. The input signals of this module are directly taken from the current feedback signal of the constant current control circuit and the voltage feedback signal of the output voltage detection circuit, and are respectively connected to a dedicated comparator or window comparator circuit. The comparator is used for rapid judgment, ensuring real-time protection and independent of the software scan cycle. When an anomaly is detected, the fault protection module feeds back the anomaly signal to the microcontroller control module. The microcontroller automatically adjusts the control strategy according to the anomaly type to ensure stable system operation. This anomaly signal is directly connected to the microcontroller's external interrupt pin or a general-purpose I / O port for rapid response.

[0023] In this embodiment, the working principle of the constant current control circuit capable of outputting multi-waveform electrical stimulation is as follows: The microcontroller control module, as the core, first generates digital instructions for the target waveform based on treatment needs. These instructions then drive the full-bridge inverter circuit via two complementary PWM signals through the bridge arm drive circuit, thereby controlling the basic frequency and shape of the output waveform. Simultaneously, the microcontroller controls the voltage regulation module via another PWM-PWR signal. This module boosts the low-voltage power supply according to instructions and finely adjusts it to the required high voltage, dynamically setting the DC bus voltage of the full-bridge circuit, thus determining the amplitude of the output waveform. To achieve high-precision constant current output, the circuit detects the actual output current through a precision sampling resistor connected in series in the output circuit. This current signal is differentially amplified by the left and right constant current control circuits and converted into a voltage feedback signal, which is sent back to the microcontroller's ADC interface in real time. At the same time, the output voltage detection circuit, through a voltage divider and voltage follower, also feeds back the output voltage signal to the microcontroller. The microcontroller continuously compares these feedback signals with internal preset values. Once a deviation is detected, such as current fluctuations caused by changes in human body impedance, it immediately fine-tunes the duty cycle of the PWM-PWR signal to change the bus voltage, thereby forming a fast and precise closed-loop control to stabilize the output current at the target value.

[0024] The technical scope of this utility model is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this utility model, and all such modifications and variations should fall within the protection scope of this utility model.

Claims

1. A constant current control circuit capable of outputting multi-waveform electrical stimulation, characterized in that, include: The microcontroller control module is used to generate two complementary PWM drive signals, a constant current control signal, and to receive feedback signals. The full-bridge inverter circuit consists of four switching devices. Its input terminal receives the two complementary PWM drive signals. Each drive signal synchronously controls a set of diagonal switching devices in the full-bridge inverter circuit to invert the DC bus voltage into an AC stimulation waveform. A constant current control circuit, whose input terminal is connected in series with the output circuit of the full-bridge inverter circuit, is used to sample the output current and generate a current feedback signal to be sent to the microcontroller control module. An output voltage detection circuit, whose input terminal is connected in parallel with the output terminal of the full-bridge inverter circuit, is used to sample the output voltage and generate a voltage feedback signal to be sent to the microcontroller control module. The microcontroller control module adjusts its output drive signal based on the current feedback signal and voltage feedback signal, and forms a closed-loop control to achieve constant current control and waveform output.

2. The constant current control circuit according to claim 1, characterized in that, The constant current control circuit includes a sampling resistor and a differential amplifier. The sampling resistor is connected in series in the output circuit, and the sampling voltage across its two ends is input to the differential amplifier. The amplified signal serves as the current feedback signal.

3. The constant current control circuit according to claim 2, characterized in that, It also includes a current detection circuit, which includes a comparator. One input of the comparator is connected to the sampling signal of the sampling resistor, and the other input is connected to a reference voltage. Its output is connected to the I / O port of the microcontroller control module, and is used to output a fault indication signal when there is an overcurrent.

4. The constant current control circuit according to claim 3, characterized in that, The output voltage detection circuit includes a resistor divider consisting of two resistors connected in series and a voltage follower. The resistor divider is connected in parallel at the output terminal, and its midpoint is connected to the input terminal of the voltage follower. The output terminal of the voltage follower outputs the voltage feedback signal.

5. The constant current control circuit according to claim 1, characterized in that, The microcontroller control module integrates a waveform control unit, which generates waveform control signals. The waveform control signals are at least one of square waves, triangle waves, trapezoidal waves, and sine waves.

6. The constant current control circuit according to claim 1, characterized in that, The four switching devices in the full-bridge inverter circuit are MOSFETs. The first PWM drive signal output by the microcontroller control module simultaneously controls the MOSFET gates of the upper left bridge arm and the lower right bridge arm, and the second PWM drive signal simultaneously controls the MOSFET gates of the upper right bridge arm and the lower left bridge arm. A preset fixed phase difference is provided between the two PWM drive signals.

7. The constant current control circuit according to claim 1, characterized in that, It also includes a voltage regulation module, whose enable terminal receives the PWM-PWR signal from the microcontroller control module, and whose output terminal provides an adjustable DC bus voltage to the full-bridge inverter circuit.

8. The constant current control circuit according to claim 3 or 4, characterized in that, It also includes a fault protection module, whose input terminals are connected to the current feedback signal and voltage feedback signal respectively. The fault protection module makes real-time judgments through a comparator, and its output abnormal signal is directly connected to the interrupt or IO pin of the microcontroller control module.

9. The constant current control circuit according to claim 7, characterized in that, The microcontroller control module adjusts the duty cycle of its output PWM-PWR signal in real time based on the current signal fed back by the constant current control circuit, thereby adjusting the output voltage of the voltage regulation module so that the current flowing through the load is stabilized at a preset value. The output voltage status is monitored based on the feedback signal from the output voltage detection circuit.

Images