KM Series PCB Mount Medical Power Supplies
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To introduce the key features of the KM series power supplies and market segments it is used in
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KM Series PCB Mount Medical Power Supplies
- 13. KM model listing
- 14. KM40 Series Installed in a Class II Application Common mode inductor L1 – 2mH Capacitors C1 & C2 – 1.5nF (must be Y1 rated)
Notes de l'éditeur
- Welcome to the training module on the KM Series PCB Mount Medical Power Supplies from TDK-Lambda.
- This training module will introduce the KM series medical AC/DC power supplies, and identify the key features of this product series and market segments it is used in.
- The design of medical approved power supplies or the integration of such supplies into medical equipment has placed demanding requirements upon design engineers. Patient and operator safety takes precedence over all other design considerations when it comes to medical equipment. While it might be tempting to think that power supplies that have been designed and certified as being safe in industrial applications might be suitable for use in medical equipment, this is not usually the case because the risks involved are different. Most of the electronic equipment used in hospitals, such as patient monitors, operate with low-level signals. Such medical equipment tends to be more sensitive to electromagnetic interference or EMI than most industrial equipment, which also makes EMC or electromagnetic compatibility compliance and performance, a key concern in medical applications. Obviously, medical equipment that has direct physical contact with patients must limit it’s leakage current to the lowest prescribed levels. Therefore, the standards for medical power supplies are much higher and are strictly enforced, as the smooth functioning of the power supply plays a vital role in the diagnosis and treatment of patients.
- When designing medical electronic equipment, a consideration for safety takes precedence over all others, so the special requirements of medical equipment must be considered. The first and most basic requirement is for effective and reliable isolation between a power supply’s input and its output, because any isolation shortcoming would result in a higher risk of electric shock. Several factors contribute to effective isolation including the spacing between conductors and electronic components, and reliable insulation. Hospital patients are often physically weak, so exposure to even small leakage currents can have an adverse effect on their well-being. All modern power supplies are of the switch-mode type because they are smaller and more efficient than the bold linear versions. Switch-mode supplies, however, generate, conduct and radiate EMI and as such require the use of EMI filters to limit unwanted electrical noise. The more effective the filter at suppressing the interference, the more leakage it is likely to produce. So it seems designers may have to accept a trade-off between EMC performance and leakage current.
- TDK-Lambda has introduced the KM Series of medically approved 15 to 40W enclosed PCB mount power supplies with single-, dual- or triple outputs. Eliminating the need for external power adaptors. The single-output models are available from 3.3V to 24V with typical efficiencies up to 83%. For the dual-output units, ranges include ±5V, ±12V and ±15V as well as 5V/12V versions. The triple-output models cover various outputs, including 5V/±12V with efficiencies up to an impressive 80%. These small, lightweight power supplies are ideal for use in a wide variety of medical equipment, in particular portable applications such as electronic blood pressure monitors and home infusion therapy equipment.
- Target markets include a variety of medical applications , such as medical analyzers, monitoring equipment, and test and measurement equipment. Having an encapsulated power supply allows for the product to be operated in a not so clean environment. A pplications include a lot of industrial applications, such as material handling, burn-in equipment, and process control equipment .
- The KM series is fully encapsulated inside a plastic case. This avoids the risk of accidental electrical shock by an operator, or dust and dirt in the atmosphere causing premature failures. The units are mounted directly on the user's PCB and can be located close to the load, reducing voltage regulation and noise pick up in the load cable wiring. The KM15 will operate from - 25 o C to 70 o C, derating linearly to a 50% load from 50 o C to 70 o C. The KM40 will operate from - 25 o C to 70 o C, derating linearly to a 40% load above 50 o C. No external airflow is required
- The KM series has been certified to the medical standards of UL60601-1 and IEC60601-1 in addition to EN60950-1 for Information Technology Equipment. Note that the input is isolated from the output by 4,000 Volts AC, significantly more than other non medical products in the market. The units will operate over a wide range of AC input voltages and from 47 to 440Hz, although safety certification only covers 50-60Hz operation. Likewise the units will operate, but have not been certified for operation, with a wide range DC inputs. No ground wire is necessary on the KM series. Next we will spend some time explaining Class I and Class II power supplies.
- You may hear manufacturers talking about Class I and Class II (Roman Numeral) power supplies. The IEC protection classes are used to differentiate between the protective-earth connection requirements of devices. There are also Class I and Class II definitions. A Class I power supply requires a ground lead for safe operation, but Class II power supplies do not and can be used with a two pronged AC line cord. The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and this is achieved without relying on an earthed metal casing. This is possible because the safety barrier is reinforced. You can see the two-square logo on the power supply, it is often used on many laptops, MP3 players and mobile phone charger power supplies.
- Many triple output power supplies have all three outputs sharing a common zero Volt line, i.e. all the outputs are connected together. The KMT models have outputs 2 and 3 separated from output 1. This gives additional flexibility when using the KMT. The figure shows an example that outputs 2 & 3 can be connected in series to give a 24V output. Improved regulation is gained on the main output and the output noise can be reduced by separating digital (5 Volt) and analogue (+/- 12 Volt) circuits.
- The KM15 is one of the smallest triple output medical power supplies available, measuring just 2.5 by 1.8 by 0.92 inches. And the KM40 is just 3.5 by 2.5 by 1.06 inches.
- Here is a breakdown of the KM series models. The first three letters indicate the number of outputs provided; the next two numbers are the power rating, either 15 or 40, representing 15W and 40W respectively; with the last five digits indicating the output voltage. A full listing can be seen on the next page.
- A total of 24 standard models are available. Custom output combinations are available, subject to non recurring engineering charges and minimum order quantities.
- The regulatory authorities, recognize different classes of medical devices, based on their design complexity, use characteristics, and their potential for harm if misused. According to the US Food and Drug Administration (FDA), the medical devices are classified into 3 classes based on the level of control necessary to assure the safety and effectiveness of the device. Class II devices are subject to special controls in addition to the general controls of Class I devices. These medical equipment include x-ray machine, surgical drapes, and PACS. External filters are needed in these applications. The diagram shows the configuration for external filters. The capacitor C1 and C2 between L-FG and N-FG must be Y1 rated. Spacing between FG and PRIMARY must be reinforced at working voltage.
- The selection and specification of power supplies for medical applications is a task that must be approached with great care; especially in these times where key safety and environmental standards for medical equipment are undergoing substantial changes that will affect large segments of the medical industry. Modern medical equipment requires power supplies that are compact, lightweight, efficient, cost-effective, RoHS compliant, reliable and super-safe. Medical equipment designers should also take care to ensure that their choice of power supplies fully satisfies, and is certified to meet, the prevailing edition of the IEC, EN, UL and CSA safety standards for medical supplies.
- Thank you for taking the time to view this presentation on “ KM Series PCB Mount Medical Power Supplies ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the TDK-Lambda site, or if you would prefer to speak to someone live, please call our hotline number, or use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.