Application example analysis of medical power supply

There have been customers bought a low-cost medical grade UPS, the power supply is 5V 200mA, hundreds of batches of the unit price is $5.
The device sells tens of thousands of dollars. The surprisingly low price of power seems pretty good. After opening this power supply, it is found that it has only one single-sided printed circuit board. In order to save the cost, the circuit board has no metallized through-hole. The circuit board adopts the surface mounting structure, and the component density is very large. The component spacing does not meet the requirements and design criteria of creepage distance specified by medical power supply and related safety management institutions. Leakage current up to 900mA, far beyond the specification limit. The creepage distance and the gap voltage can not reach the voltage used in the general power supply. The spacing between the high pressure regions is only 0.5mm, and the flux resistance is used to improve the dielectric resistance. The pin spacing of the MOSFET should have increased to increase creepage distance, but this power supply does not deal with this, probably because of the cost of manufacturing and this will take up more space. The aluminum fin is inserted into the circuit board by some claws, and then welded and fixed. Once the treatment is not correct, the radiator is easy to loose. MOSFET in flyback circuit is fullpak package with unkown manufacturer, there is a silicone jacket, and with insulating tape on the heat sink, which hinders the contact between device and radiator, which will have thermal stability may produce serious problems, that is heat sink is still cold when MOSFET has been hot. This power supply meets the commercial EMI-RFI requirements, but does not meet the medical power requirements.
This power has some other problems, such as the rosin joint in power supply everywhere. When using, even if the assembly is correct, also cause failure at any time. Although this power supply is sold as a medical UPS, it is not designed in accordance with the medical requirements. In addition to the input voltage and output voltage and current, there is no relevant documents and technical indicators. In addition to the surprisingly low price of this power supply, other performance are far from the requirements of medical power supply.
In the selection and purchase of hospital UPS, we must consider the risks, must be purchased from reputable manufacturers that provide quality and reliability standards and requirements.

SOROTEC GP9335C 10-800KVA Low Frequency Online UPS

■Use advanced 6th generation DSP and full digital control technologies to realize higher system stability.
■Output power factor is 0.9, carrying capacity than conventional 120 kva UPS with 10% above, as users reduce investment cost.
■Advanced distributed active parallel technology can realize parallel operation of 6PCS 120 kva UPS units without the need of centralized bypass cabinet.
■6-inch extra large LCD that can display 12 language ( Chinese ,English,Russian,Spanish,French and so on).
■Extra wide input voltage and frequency range make it adapt to severe power grid environment.
■Intelligent battery management maintains battery automatically to prolong the battery life.
■Standard input/output filter improves the system EMC performance.
■Extra strong capability to withstand output overload and short circuit, ensuring the system stability and system safety under extreme conditions.
■Layered independently-sealed ventilation channel and re-dundant fan, circuit boards with protective paints and a dust filter embedded make it highly efficient to dissipate heat and protect the product effectively under severeenvironment.

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