The medical equipment industry is an emerging industry related to human life and health. In the past ten years, the developed countries in the world have maintained a high annual market growth rate, which is known as the sunrise industry. With the improvement of medical standards, more and more advanced medical equipment is widely used in various medical situations. As an important part of medical equipment, power supplies have more stringent requirements than other types of power products. This article focuses on the special requirements of medical power supplies and the technical characteristics of Jinshengyang's high-quality medical AC-DC products.
Special requirements for medical power
Currently, most medical devices use switching power supplies. With the development of electronic technology, switching power supplies are not only greatly reduced in size, weight is reduced, but energy consumption is greatly reduced, and reliability is improved. The use of AC-powered medical diagnostic, measurement, and therapeutic equipment may expose patients and medical personnel to potential hazards such as electric shock, burns, internal organ damage, and arrhythmia due to leakage currents due to improper grounding and electrical insulation. .
Due to the special use environment of medical equipment, medical power products have more stringent requirements in terms of safety and reliability. For example, the insulation and leakage current requirements of IEC 60601-1 safety regulations, or their associated standards, such as: EN60601-1, UL60601-1, and CSA22.2, 601.1 M90, must be met. Table 1 summarizes the safety requirements for IEC 60601-1 medical equipment.
Table 1 IEC60601-1 safety standard requirements
On the other hand, electromagnetic radiation and electromagnetic radiation protection of medical devices are an important parameter standard for medical power supplies , involving surge and transient current strength, electrostatic discharge (ESD) levels, and radio frequency interference (RFI) protection capabilities. Many medical applications involve RF therapy devices or non-invasive electronic surgical instruments, so the power supply must be immune to interference and unaffected.
Qualified medical power supplies shall comply with the EN60601-1-2 standard in accordance with EMC related technical requirements. Not only that, the medical power supply must also meet IEC61000-4-2 (electrostatic protection capability, required to reach 3kV), IEC61000-4-3 (radio frequency radiation protection capability, required to reach 3V/m), IEC61000-4-4 EFT (voltage transient) Variable capacity, required to reach 1kV), IEC61000-4-5 (mains surge current capability, required to reach 1kV and 2kV), IEC61000-3-2 (mains line harmonic requirements), IEC61000-3-3 (power line flash Variable requirements), and EN55011 (Class A product or B product radiation restrictions) and other requirements.
In addition, there are some special requirements related to specific applications. For example, the system may be used on an ambulance, and voltage shocks may occur. This power supply should at least comply with IEC 68-2-29; some devices are portable devices. It may be used on helicopters, and random vibrations may occur. Such power supplies shall comply with MIL-STD-810E.
Jinshengyang LD series product features
Jinshengyang Company is committed to the development of medical ACDC power supply. Currently, it has LD05 and LD10 series products. The principle block diagram of the product is shown in Figure 1. The product is always aiming at high reliability during the design process, and this is reflected in every aspect of the design.
Figure 1 LD series product block diagram
First, the reliability of the product control chip plays a crucial role in product reliability. Our products use ON Semiconductor's PWM control chip. Because the chip is very powerful, only a few external components are needed to form a complete switching power supply, which greatly simplifies the product design and greatly improves the sense. Product reliability. In addition, the chip's standby power consumption is very low, providing a solution that meets the standards of the US Energy Star and the European Blue Sky, and meets the latest recommendations of the International Energy Agency (IEA) under no-load conditions. The short-circuit protection function of the chip can also detect the occurrence of a short circuit by continuously monitoring the condition of the feedback line, and immediately reduce the output power, thereby protecting the entire power supply and the subsequent stage circuit. Once the short circuit condition disappears, the controller resumes normal operation. This function also greatly improves the reliability of the product under abnormal conditions.
Secondly, we have done a lot of useful research on the thermal design of the module power supply. MTBF is a measure of power supply reliability, and the most important factor affecting MTBF is the temperature of the component. Therefore, to improve the reliability of the power supply, it is important to keep the temperature low. The simulation method helps to make some abstractions more intuitive, so we introduced the electrothermal model. The so-called electrothermal simulation uses a thermal circuit to simulate the heat dissipation circuit of an electronic device, and uses electrical parameters to simulate the transfer of heat. Specifically, the current in the circuit is used to simulate the heat in the thermal path (in the calculation, the dissipated power PD of the commonly used semiconductor device is used instead of the heat Q), and the flow of the current is used to express the transfer of the heat flow. The voltage U corresponds to a temperature difference ΔT between the device temperature and the ambient temperature, and the resistance R corresponds to the thermal resistance Rth. Of course, in addition to the simulated heat transfer, a large number of high and low temperature reliability tests are also used to verify and improve the thermal design of the product during the design and verification process.
Third, the strict requirements on the EMC characteristics of the product ensure the reliable operation of itself and the system. People are paying more and more attention to the EMC of electronic products, and countries and organizations around the world have also made corresponding regulations on electronic products. Typical standards include: Federal Communications Commission (FCC) Rules and Regulations Part 15; IEC61000 part of TC77 in the International Electrotechnical Commission; CISPR22 (Information Technology Equipment) of the International Committee on Radio Interference (CISPR); EN55022 of the European Union (information) Technical equipment); China's GB9254-1998 (Information Technology Equipment) was converted from CISPR22 of CISPR.
Generally, there are three conditions for forming electromagnetic interference: a source for transmitting electromagnetic interference (noise source), a path for transmitting electromagnetic interference (noise coupling and radiation), and a subject for receiving electromagnetic interference (disturbed device). Therefore, the suppression of electromagnetic interference of power products must also start from these three aspects. The following methods are used to solve the EMC problem of the product: 1. Selection of EMI filter; 2. Optimization of input and output filter network design; 3. Application of buffer circuit; 4. Minimize high-frequency loop area; 5. Optimization Ground wire design; 6. Shielding application.
In addition to the high reliability guaranteed in the design, the LD series module power supply products have the following features:
Small size and high power density. Jin Shengyang's LD series power supply is small, among which: LD05 series power supply has an output rated power of 5W, universal voltage input, and the volume is 50.08*25.4*15.16mm. The output power rating of the LD10 series power supply is 10W, the global universal voltage input, the volume is 53*28*19mm, as shown in Figure 2. This type of small-volume power supply saves a lot of component space for small medical devices, thus making it possible to miniaturize the device.
Figure 2 LD10 series product dimensions
Good safety performance. The products are designed in strict accordance with the requirements of medical power supply. In the safety design, the distance between input and output is more than 8mm, and the withstand voltage between input and output reaches 4000VAC/1min. The leakage current of the input to the output is also small. The LD05 series has no internal safety capacitor design, so the leakage current is almost zero; the LD10 series is also only 100μA or less. The LD05 and LD10 series power supplies have passed the EN60601 medical certification (certificate number: E/CE2995090218023, E/CE3180090723209) and UL60950 safety certification (certificate numbers are: E235235-A17-UL-1 and E235235-A18-UL-1 respectively) ).
EMC performance is good. The product passed the comprehensive EMC test of the Saibao Laboratory of the Fifth Electronic Research Institute of China and obtained the certificate. See Table 2 for details.
Table 2 Product EMC Test Standards and Results
Complete application guide. In order to enable customers to better use the product, the LD series products provide detailed and typical application circuits, as shown in Figure 3 (specific parameters can participate in the product technical manual). Customers can choose the right application circuit according to their own needs.
Figure 3 Typical application circuit
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