Electromagnetic Compatibility Solutions for Electronic Circuits of Medical Electric Chairs

Electromagnetic Compatibility Solutions for Electronic Circuits of Medical Electric Chairs

Circuit design solutions for EMC

Hardware Circuit Design Strategies

1.Grounding Design

Adopt reasonable grounding methods, such as single-point grounding, multi-point grounding, or hybrid grounding. For the electronic circuits of medical electric chairs, the part of the drive circuit with relatively high power can use single-point grounding to reduce interference current in the grounding loop; while the signal processing circuit part, due to its high requirement for signal accuracy, can adopt multi-point grounding to reduce grounding resistance, improve anti-interference capability, and ensure the stable operation of the equipment in complex electromagnetic environments.

2.Shielding Technology

Use metal shields to shield circuit modules that are susceptible to interference or generate interference. For example, wrap the motor of the electric wheelchair with a metal shield to prevent the electromagnetic radiation generated during motor operation from spreading outward and avoid interference to other circuits; at the same time, use shielded wires for sensitive signal transmission lines to prevent external electromagnetic interference signals from coupling into the transmission lines, ensuring the accuracy of signal transmission.

3.Filter Circuit Design

Filter circuits are installed at the input and output ends of the power supply as well as on the signal transmission lines. A low-pass filter is added at the power input end to filter out high-frequency interference signals on the power lines, ensuring that a clean DC power supply is provided for the equipment; on the signal transmission lines, appropriate filters, such as band-pass filters, are designed according to the frequency characteristics of the signals. This allows useful signals to pass through smoothly, blocks interference signals in other frequency bands, and improves the anti-interference performance of the circuit.

EMC and Reliability Design of AC Power Interface

AC power interface: used to connect to an external 220V AC input.

EMC and Reliability Design of 12V/24V Vehicle-mounted Power Interface

DC power interface: used to connect to an external 12V/24V vehicle-mounted power input, supporting offline use (e.g., when the patient is moving).

EMC and Hot-Swap Reliability Design of GPIO/UART/I2C Interfaces

GPIO interface (General Purpose Input/Output): used to connect external devices such as sensors and actuators, supporting custom programming control.

EMC and Hot-Swap Reliability Design of SPI Interface

SPI interface: a high-speed serial communication interface used to connect memory chips, display screens, etc.

EMC and Hot-Swap Reliability Design of JST Interface

JST interface: a dedicated interface for connecting devices such as sensors.

EMC and Hot-Swap Reliability Design of Pin Header Interface

Pin header interface: used for plugging wires or expansion boards to achieve function expansion.

MCU-driven BLDC motor module

MCU Interface: The control of BLDC (Brushless Direct Current Motor) by MCU usually involves various types of interfaces, with common ones including PWM output interfaces, Hall sensor input interfaces, etc.

Pin Definition: The MCU will output 6 channels of PWM signals to control the upper and lower bridge arms of the three-phase bridge; in addition, there will be 3 channels of input interfaces connected to Hall sensor signals to obtain the position information of the motor rotor and achieve correct commutation.

EMC and Hot-Swap Reliability Design of RS485 Interface

RS485 interface: RS-485 is a serial communication standard that allows multiple devices to communicate via the same serial bus. It is suitable for medium and long-distance communication, with good anti-interference ability and stable data transmission performance.

EMC and Hot-Swap Reliability Design of Ethernet Interface

It supports wired network connection, providing a stable network link for the machine and enabling remote control and data interaction. Via Ethernet, the machine can upload work data to the cloud in real time and receive remote commands, realizing intelligent remote operation. Its transmission rate can reach 1000Mbps or even higher, meeting the machine's requirements for high-speed and stable data transmission.

Software algorithm optimization assistance

1.Anti-interference programming

In software programming, anti-interference algorithms are incorporated.

For example:- Digital filtering algorithms are applied to process the collected sensor signals, removing noise interference in the signals and enhancing signal reliability.

- During the transmission and reception of control commands, methods such as checksum and CRC (Cyclic Redundancy Check) are used to ensure the accuracy of data transmission, preventing data errors caused by electromagnetic interference, thereby guaranteeing the control precision and safety of the electric chair.

2.Fault diagnosis and self-recovery

Develop a fault diagnosis program to monitor the working status of the electronic circuits of the electric chair in real time.

When abnormal conditions caused by electromagnetic interference or other reasons are detected, it can quickly locate the fault point and take corresponding self-recovery measures, such as re-initializing the circuit, adjusting control parameters, etc., so that the equipment can resume normal operation as soon as possible, and reduce the inconvenience and danger to users caused by faults.