How to Improve the Safety of Medical Device Power Systems?

January 26 15:16 2022
Under the global impact of the health crisis in 2020, the industry has faced challenges in many ways. The medical industry is growing rapidly, providing solid support for our fighting against the virus and the key to solving public health problems in the future. MORNSUN power provides a supply of products with stable and excellent performance to help improve the reliability of the devices and system.

With the continuous development of the medical industry, the technology and quality of medical equipment is improving, which has led to the continuous innovation and development of its upstream industry chain products. As the “heart” of the equipment, the demands and requirements of medical power supply are also increasing. How to match the development of the medical industry from the aspects of product performance, delivery, quality, safety regulations, certification, and so on is what medical power supply suppliers need to consider and achieve.

1. “Safety” and “Compliance”: the Foundation of Medical Device Power Supply

The most important criteria of medical device power supply are safety and compliance. Safety depends on whether the power supply can meet the requirements of medical industry certification standard EN60601, including leakage current, safety distance, etc. Compliance is reflected in whether the production and materials can ensure sufficient consistency, whether the process control is reasonable and effective, and whether the outflow of nonconforming products is strictly prohibited.

Safety standards include:

IEC 60601-1 General Requirements for basic safety and basic performance;

IEC 60601-1-2 electromagnetic interference requirements and tests.

Compliance standards include safety and EMC. Safety regulations are mandatory criteria, and whether or not the product meets the standard requirements depends on its design. EMC is a compatible criterion. The power supply itself must meet the requirements. At the same time, it is also required to consider the comprehensive design of the whole system of the layout, connecting wire, shielding, and so on. In particular, vitro diagnostic equipment includes many components such as circuit, waterway, structure, connecting wire, display, electric, heating, cooling, and so on, so that EMC should be considered at the beginning of the design to avoid expensive testing and rectification costs in the later stage.

2. How to Design High-Quality Medical Device Power Supply: a Brief Analysis of Design

Meet medical certification EN60601

Taking the LOF series as an example, this product has a 5-year warranty and its safety specification meets the IEC / EN / ES 60601 Standard, the leakage current is less than 0.1mA which is suitable for BF types of medical devices, and the isolation safety distance (creepage and clearance) meet the medical standard.

Outstanding EMC design

Medical power supply requirements of ultra-low leakage current, high safety distance and ability of high-voltage withstand and miniaturization, and high power density design are mutual constraints. Most products on the market compromise on EMI to meet only the CLASS A standard, which greatly increases the risk of interference from power supply products to other functional circuit modules inside the medical device.

The conducted emission and radiated emission of the LOF series meet class B:

A. The input EMI filter module, the PFC module, and the main power module are respectively arranged in a centralized manner and effectively isolated by a radiator (grounding), which minimizes EMI interference, reduces some EMC components, and optimizes space.

B. The input terminal is designed with a flat line common mode inductor, fully automatic winding and without overlapping, with a small capacitance between turns, and has a good impedance balance. EMI performance is much better than the traditional magnetic ring common mode inductor and provides small size and beautiful appearance.

C. It is designed with PFC function and is easy to meet the standard of IEC / EN61000-3-2 CLASS A and CLASS D. The electrostatic requirements meet the latest standard of 8kV/15kV.

The conducted radiation waveform is as follows, with sufficient margin:

When designing a good product, the process of improving production efficiency and reducing process complexity will be considered in advance, which can not only reduce labor cost but also greatly improve production efficiency and product quality, thus reducing the follow-up debugging of medical devices.

LOF series with new design controls the product quality precisely from the details:

1. Our transformer adopts an open-frame design, no flying wire, and the common-mode inductor with the base design, which reduces the complexity of production and improves production efficiency. 

2. The traditional compact design leads to the electrolytic capacitor being heated up by the transformer and diode nearby. The thin & long capacitor we choose can keep away from the heat source and solves this problem well.  

The special application environment of medical equipment determines its preciseness. When selecting a medical power supply, it is necessary to consider not only safety regulations and EMC performance, but also the compatibility between structure and EMC in the design stage, as well as product reliability, supply stability, cost, technical support, and other factors.

3. Typical Application Cases of Medical Device Power Supply

Typical scheme I: Sputum extractor

The main inductive loads of the Sputum extractor are relays, motors, pumps, etc., which are prone to spike interference. It is required that the power supply has sufficient anti-interference ability to ensure that the power supply can work stably and reliably for a long time.

 

The front end of MORNSUN’s LOF series power supply has more than two levels of differential mode and common mode filtering, which can effectively suppress peak interference. The power taken from the LOF output to supply inductive loads has been effectively filtered to eliminate the interference, which may result in conducted emission and radiated emission not passing the standard if it leaked into the supply network.

It should be noted that loads powered by mains power supply directly and loads with long connecting lines need to further increase their filtering and reasonable wirings to avoid interference emitted from the connecting lines.

Typical scheme II: Ventilator

The ventilator is a product contact directly with patients, and the safety protection level shall meet the isolation requirements of 2x MOPP. MORNSUN LO-MU series complies with IEC60601-1, EN60601-1, and other medical standards, and meets 2x MOPP. The patient leakage current is less than 75uA, and the noise is less than 25dB, ensuring a quiet and comfortable environment.

 

Meanwhile, MORNSUN’s LOF series is a high-power AC / DC power supply with a PFC function, which meets the harmonic requirements of IEC 61000-3-2.

 

4. Deep-Insight of Industry Trends and Market Demands

Safety and reliability are the primary concerns for the requirements of medical device power supply. Secondly, EMC, delivery, cost, and other factors need to be considered. Based on the comprehensive power supply R&D platform, MORNSUN works closely with clients and makes research on the market demand and requirements of the medical device, response quickly, is committed to providing more reliable and stable power solutions to promote further development of the medical industry.

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