The isolated power supply uses a transformer to reduce the voltage to a lower voltage through a transformer and then rectify it into a DC output for power supply. Because the main coil of the transformer is subjected to 220V voltage, the secondary coil only bears the low AC voltage of the output, and the primary and secondary coils are not directly connected, so it is called an isolated power supply.
Communication port isolation power applicationThe isolation of RS-232, RS-485, CAN-bus and other communication ports is inseparable from power isolation and electrical isolation. The most common method of power isolation is to use an isolated power module. The isolated power module not only separates the system ground from the communication ground, but also effectively resists interference, and also has the function of voltage conversion.
Solution recommendation: isolation circuit with discrete components
The isolated power supply module is used to supply power to the isolated communication interface, which can effectively block interference and protect the front-end circuit of the system. To better suppress high-frequency transient interference, a TVS tube can be connected to the input of the isolated converter as shown. When selecting a TVS tube, the parameters such as the withstand voltage and clamping voltage of the TVS tube should be considered comprehensively, and a reasonable model should be selected. If the power of the power module is relatively large, and the power consumed by the communication interface is less than 10% of the maximum output power of the module, it is recommended that the user connect a dummy load in parallel with the output, as shown in Figure 1.1, R1 to ensure that the power module works well. Under load conditions.
Most of the power modules suitable for communication isolation are constant voltage input isolation and unregulated output series, such as TEN-POWER's BS-1W series. This series of modules is available in a wide range of models, including SIP, DIP and other packages. The user can select the appropriate model according to the conditions of use to meet the requirements of volume, weight, performance, portability and the like.
Medical isolated power supply design and application in a hospital1. Medical isolated power supply system
1.1 isolation transformer
The isolated power supply provides isolated safety power to the important places of the hospital through the isolation transformer, and the transformation ratio is 1:1. The transformer's primary coil turns are equal to the secondary coil turns, while the primary and secondary coils are highly insulated and an electrostatic shield is placed to minimize electromagnetic interference between the two windings.
1.2 Insulation monitor
The insulation monitor is used to monitor the insulation status of the IT system to the ground. When the system has an insulation fault, it can issue an alarm signal in time to remind the staff to handle it according to the actual situation. At the same time, the transformer load current and transformer winding temperature can be monitored to ensure reliable and normal operation of the isolation transformer.
1.3 centralized alarm and display
It can display the monitoring data of the current insulation resistance and transformer load rate of the medical insulation monitor in real time, and emit an audible and visual alarm signal when the system fails, and can set the alarm threshold of the insulation monitor remotely through the alarm and display. The device is mainly installed in the operating room or the information control panel in the intensive care unit to help the medical staff understand the operating status of the isolated power system and the type of failure in the event of a system failure.
1.4 Insulation fault location
The insulation fault location is set by the fault locator and the test signal generator. The high-sensitivity transformer is used together with the high-precision signal detection circuit to detect the signal injected into the system by the test signal generator and accurately locate the loop where the insulation fault is located. It is convenient for staff maintenance and overhaul.
2 The necessity of using medical isolated power
1) Effectively guarantee the normal operation of medical equipment.
2) Preventing leakage currents from other power supply circuits from entering the medical equipment in special places such as operating rooms, ICUs, and CCUs through the grounding line poses a danger to patient safety.
3) Medically isolated power supplies reduce the potential for ground faults in various medical devices. Once the various medical devices connected to the isolated power supply have a ground fault, because they cannot form a loop to the ground, they can only produce a small capacitive leakage current, which greatly protects the patient from leakage current.
4) When the medical equipment is insulated, the neutral point of the power supply is not grounded. When the first point of grounding insulation fault occurs on the load end, it will not form a loop due to its grounding, and will only generate a small leakage current. As a result, the protection device (such as empty opening) is cut off from the power supply, and the operating room does not have a sudden power failure, thereby ensuring the continuity of the power supply in the operating room.
5) The medical isolated power supply reduces the leakage current to the ground, thus improving the fire safety.
6) When the hospital is in trouble-repairing and repairing medical equipment, it is often necessary to contact the components in the circuit or the ground wire in the circuit under the power-on state. The use of the medical isolation power supply can prevent the risk of electric shock of the hospital equipment maintenance personnel.
3. It is recommended to connect to the electrical equipment of the isolated power system grid.
The medical equipment recommended for access to the isolated power system grid includes: high-frequency electric knife and other high-frequency surgical equipment, defibrillator, ventilator, anesthesia machine, constant temperature incubator, dialysis equipment, monitor, infusion pump, injection Pump, cardiopulmonary machine, extracorporeal circulation machine, etc.
4, medical isolation power supply system configuration plan
The predecessor of Shandong Cancer Hospital (Shandong Cancer Research Institute) is the Jinan Sanatorium of the Provincial Post and Telecommunications Association. It was established in 1958 and was established as a cancer specialist hospital in 1971. It is currently a Grade III hospital and a research institute in Shandong Province. Master's degree in clinical oncology, number of doctoral students, and national drug research base. The hospital ordered seven sets of five-piece products at Ankerui Electric in September 2013.
4.1 Operating room configuration plan
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