Electronic equipment is used increasingly in different medical and home healthcare environments and product designers will be familiar with the electrical safety standards that must be complied with: IEC 60601-1:2005 with its collateral documents and national variants, including EN 60601-1:2006 in Europe.
When considering a product’s AC/DC power supply requirements, there has been plenty of guidance written about the application of the latest version of the safety standard, with its reference to ‘measures of protection’ (MOPs) in operator and patient environments. It might seem wise to simply specify a power supply with the highest level of safety - 2 Measures Of Patient Protection, (MOPPs), rated at the maximum supply voltage and with leakage current no more than specified for the closest patient contact, type CF (cardiac floating), where electrical connection to internal organs is expected for monitoring or stimulation. In battery-operated equipment, it could also be thought that the safety standards are not applicable. There are instances however where a fully certified AC/DC on its own is insufficient but in other cases could be over-specified and examples where battery-operated equipment needs internal safety isolation.
Taking the case of AC-powered equipment, there must be a minimum of 2 x MOOPs or MOPPs isolation from AC line to output, depending on whether the equipment is expected to be used in an ‘operator’ or ‘patient’ environment respectively. However, patient-connect outputs must also be isolated from ground by a minimum of 1 x MOPP, to cover the possibility that the patient could become electrically ‘live’ from other faulty equipment and lethal current could then flow through the patient to earth. An additional isolated DC/DC converter providing power to the patient-connect circuitry can help in this situation; if it has suitable medical-grade isolation, it can enable an AC/DC with only 1 x MOOP output isolation to ground to be used in a patient-connect application.
When considering a product’s AC/DC power supply requirements, there has been plenty of guidance written about the application of the latest version of the safety standard, with its reference to ‘measures of protection’ (MOPs) in operator and patient environments. It might seem wise to simply specify a power supply with the highest level of safety - 2 Measures Of Patient Protection, (MOPPs), rated at the maximum supply voltage and with leakage current no more than specified for the closest patient contact, type CF (cardiac floating), where electrical connection to internal organs is expected for monitoring or stimulation. In battery-operated equipment, it could also be thought that the safety standards are not applicable. There are instances however where a fully certified AC/DC on its own is insufficient but in other cases could be over-specified and examples where battery-operated equipment needs internal safety isolation.
Taking the case of AC-powered equipment, there must be a minimum of 2 x MOOPs or MOPPs isolation from AC line to output, depending on whether the equipment is expected to be used in an ‘operator’ or ‘patient’ environment respectively. However, patient-connect outputs must also be isolated from ground by a minimum of 1 x MOPP, to cover the possibility that the patient could become electrically ‘live’ from other faulty equipment and lethal current could then flow through the patient to earth. An additional isolated DC/DC converter providing power to the patient-connect circuitry can help in this situation; if it has suitable medical-grade isolation, it can enable an AC/DC with only 1 x MOOP output isolation to ground to be used in a patient-connect application.