In today's society, with the continuous advancement of science and technology, more and more modern medical devices have developed rapidly. Especially for electronic instruments that directly contact the human body, in addition to the increasingly high requirements on the performance of the instrument itself, Human safety considerations are also getting more and more attention, such as: heart puncture monitors, ultrasound, maternal and child monitors, baby warmers, life monitors, and other instruments that are in close contact with the human body, that is, patients The instrument must not cause any electric shock or any other danger to the human body due to the use of the instrument. So, when choosing the most relevant medical power supply, what should we pay attention to? The choice of medical power supply Medical electronics, unlike other electronics and power electronics that are positioned in the mass market and in consumer electronics and other low-cost product applications that care about cost, medical electronics have far more rules to follow. If the designer is responsible for system power design, the first question to be considered for the system power supply part is: to buy or manufacture related solutions? Because the output of medical electronics is generally relatively low, designers must consider the issue of purchase or self-made. Designers of medical electronics rarely consider designing offline power supplies themselves. Because the investment required for such special design and testing does not match the final output scale; equipment manufacturers will find that product output is difficult or impossible to share the investment made in the design stage. Therefore, it is more cost-effective to directly purchase power supplies from companies that already have corresponding professional design capabilities and test technology. 1. Price In the design of commercial applications, if the quality is guaranteed, it is easy for people to directly select the lowest-priced power supply product after shopping around. At this time, the lowest-priced but "passable" product is often the winner, while the best product is not popular. This is not bad for disposable electronic products that will soon be discarded or do not need to be repaired, but if designers choose one of these power sources to use them in medical systems, what are the risks? Medical electronics are very valuable , Need to complete some key tasks. If the medical system breaks down, the consequences are more than just missing a game or taking the wrong train. The normal operation of medical equipment is critical to life and death, especially the power supply of medical equipment, must comply with relevant regulations on safety, leakage, EMI-RFI radiation and protection. These standards and related safety regulations constitute a set of strict normative requirements. The power supply used in such demanding application systems must comply with strict specifications on insulation measures to prevent electric shock to patients and medical personnel. EMC is also a key issue, including how to reduce electromagnetic radiation and how to protect it. Therefore, for the design of medical power supply, the quality and reliability of the product must be the first choice. Often, designers confuse commercial power supplies with medical power supplies, and manufacturers that manufacture a variety of low-cost power supplies for the mass market may sell these commercial power supplies as medical power supplies without modification. In this regard, buyers must be careful because choosing such a power supply product because of greed is cheap will cause dire consequences. Therefore, designers need to understand the relevant rules and regulations. So, what issues will be involved in choosing medical power? The power of medical equipment must comply with the relevant regulations on safety, leakage, EMI-RFI radiation and protection. There are other questions, including whether the products are produced by GMP certified factories? 2. GMP qualification The United States Food and Drug Administration (FDA) requires medical products to be manufactured in factories that are GMP qualified (that is, have good manufacturing practices). This is a set of quality certification system that should be required by manufacturers in addition to the traditional ISO9000 certification to prove that its quality control procedures comply with GMP regulations. Similarly, China also has strict control of medical power supply, for example, it must meet a series of requirements such as CE and UL medical certification. The GMP regulations stipulate that manufacturers must have component quality control procedures and have relevant documentation. When choosing a medical power supply, can you ask the manufacturer whether there are component quality control regulations? Are there quality data and test documents? What is the procedure and the relevant documents are required. Manufacturers are required to produce documents that can prove the quality and reliability of their products, and reputable manufacturers will be happy to provide them. We found that many low-cost manufacturers are using non-branded, non-manufactured power supply products or counterfeit power supply products, which brings many problems to the final medical electronics OEM. If the manufacturer can't take out the relevant certification documents, and they just change the power supply of the POS terminal and sell it as a medical power supply, then such a product will only make the user lose the gain. Therefore, for the selection of a good medical power supply, GMP qualification can prove its product production and quality control accordingly, but is such a product a good product? No, we must also grasp the performance parameters and reliability of the product. That is, whether the product has passed some international general specifications. EN60950 is an international safety standard that is suitable for universal power supplies. Medical power supplies also need to meet the minimum basic requirements in this specification. However, the international safety standard for medical power supplies is the stricter IEC601-1 A2, and there are three versions according to regions: EN60601-1 in Europe, UL2601-1 in the United States, and CSA22.2 No 601.1 in Canada. These specifications cover technical indicators such as electric shock protection, fire protection and machinery, as well as creepage distances and clearances, and high-voltage insulation and other test indicators. The medical power supply must use appropriate design techniques to ensure that it can still work stably when the input is abnormal, and can work under certain special environmental conditions (such as oxygen and / or anesthetic gas). In these applications, fire protection is also an important issue 3. Leakage current Leakage current is the current that flows to ground through the protective ground conductor. Without grounding, if there is a conductive path (such as a human body), this current can flow from the surface of a conductive or non-conductive component to ground. There is always external current in the safety ground conductor. Generally, the upper limit of leakage current of medical power supply is one tenth of ordinary power supply All power supply leakage current specifications of the IEC601 standard are much stricter than non-medical power supplies. The technical indicators define several different and most critical leakage currents, such as: ground leakage current (flowing into the ground along the grounding body) and casing leakage current (flowing into the ground from the casing through the patient). The IEC601 standard defines different maximum leakage currents for the following three main types of equipment power supplies: Class B: Equipment that does not come into contact with the patient ’s body, such as a laser treatment device Class BF: Equipment to be in contact with the patient ’s body, such as ultrasound, various monitors (including EGC equipment), and operating tables Class CF: Equipment to be in contact with the patient's heart, such as a cardiac puncture monitor. People often misunderstand that these types of devices have different leakage current specifications. In fact, the allowable leakage current of these types of equipment is the same. The North American index requirements are stricter than the allowable leakage current specified in European EN60601-1. For example, Europe allows 0.5mA, while the United States and Canada only allow 0.3mA. Therefore, medical device designers need to pay attention to where their products will be sold. And BF or CF type equipment (commonly known as "contact human body" equipment) also requires additional insulation measures to insulate the patient from ground, signal ports and power output. This is to protect the patient in the event of an unexpected failure of the equipment and to keep the leakage current on the patient within the limits specified by the standard. This insulation can also be achieved by other parts of the final equipment, such as plastic probes or bushings with sufficient insulation properties. However, in applications that require energizing the patient, one of the treatment methods is to use an AC / DC power supply that complies with the IEC601-1 standard to power one or more isolated DC / DC converters, that is, to add a second level of insulation protection. Therefore, the DC / DC converter must be carefully selected to ensure that the insulation requirements can be met. Since medical equipment is often connected directly to the patient, and will form a conductive path through the skin or even the subcutaneous connection, the leakage current must be as low as possible, the insulation must be reliable, and there must be no sneak current. Multilayer Piezoelectric Speaker,New Piezo Speaker,Piezoelectric Speaker Sounder NINGBO SANCO ELECTRONICS CO., LTD. , https://www.sancobuzzer.com
June 17, 2020