Medical Electronics


patient auxiliary current, and patient leakage current represent a challenge for designers. They must ensure that the power supply provides the required safety isolation while minimising leakage currents under normal operation and protection under fault conditions by isolating the patient from the ground.


Figure 3: An approved DC/DC converter (right) can be used for voltage regulation to the applied part while providing secondary isolation for 1 x MOPP and minimising potential patient leakage current. (Image source: XP Power)


MOOP Insulation Basic (1 x MOP)


Double of Reinforced (2 x MOP)


4.0 mm 6.4 mm


Air clearance Creepage distance


2.0 mm 3.2 mm Test voltage 1,000 VAC 3,000 VAC MOPP


Air clearance Creepage distance


2.5 mm 5.0 mm


Table 1: Shown are the air clearance, creepage distance, and test voltages for basic (1 x MOP) and reinforced (2 x MOP) insulation in both MOOP and MOPP applications. (Table source: XP Power)


product’s normal use. The standard defines applied parts according to the type of patient contact and the nature of the medical device. Type B classification is given to applied parts that are generally nonconductive and may be connected to ground. Type BF (body floating) is given to applied parts that are electrically connected to the patient and must be floating and separated from ground. Type BF does not cover applied parts with direct contact to the heart. Type CF (cardiac floating) classification is given to applied parts suitable for direct heart connection. Type CF applied parts must be floating and separated from ground. Patient-connected medical devices are required to provide means of protection (MOP) to prevent applied parts (and other accessible parts) from exceeding the limitations of voltage, current, or energy. A compliant protective ground connection provides 1 x MOP, basic isolation also provides 1 x MOP, and reinforced insulation provides 2 x MOP. MOP can be further categorized as Means of Operator Protection (MOOP) and Means of Patient Protection (MOPP). In devices intended


Model Number


D1 C1(1)


for patient connection, 2 x MOPP are required. Power supplies for medical devices with Type BF and CF classifications must provide 2 x MOPP from primary to secondary and 1 x MOPP from primary to ground. Additional safety isolation from any secondary output of the power supply to ground must also be rated at 1 x MOPP for the highest-rated incoming AC line voltage. Table 1 shows air clearance, creepage distance, and test voltages for basic (1 x MOP) and reinforced (2 x MOP) insulation in both MOOP and MOPP applications.


In addition to MOP for MOOP and MOPP applications, the power supply for a medical device must be designed to limit the touch current, patient auxiliary current, and patient leakage current. The maximum allowable values for the touch current are 100 microamperes (μA) in normal conditions and 500 μA in a single fault condition (SFC). This requirement effectively limits the system ground leakage current to 500 μA in normal operation.


The requirements for touch current,


Figure 4: Shown are recommended EMC filter circuits for surge and EFT and EMI class B for use with JMR10 series DC/DC converters. (Image source: XP Power)


4.0 mm 8.0 mm Test


voltage 1,500 VAC


4,000 VAC


Using a DC/DC converter as a second isolation stage


The design challenges of special medical requirements can be mitigated by carefully selecting a DC/DC converter to introduce a second isolation stage. The addition of this stage provides basic isolation at AC line voltage. It also minimises input-to-output capacitance (to around 20 to 50 picofarads (pF)), which in turn reduces the potential patient leakage current to just a few microamperes (Figure 3).


For example, the XP Power JMR series 10 watt DC/DC converters described above feature IEC60601-1 medical safety agency approval, 2 x MOPP 5 kilovolt (kV) AC reinforced isolation, 17 pF isolation capacitance, and 2 μA patient leakage current, enabling easy integration into a wide range of BF and CF medical applications. EMC filtering, required to enable the end product to meet the requirements of IEC 60601-1-2, can be added to the circuit between the medical device system and controls and the DC/DC converter without compromising isolation or low-leakage currents. Figure 4 illustrates recommended EMC filter circuits for surge and electrical fast transient (EFT), and EMI Class B. Table 2 shows recommended component values for these circuits when using the JMR10 series devices with input voltages of 12 V, 24 V, and 48 V.


Conclusion C2, C3 L1 JMR1012XXX SMDJ26A 470 μF / 100 V MLCC, 22 μF, 35 V 2.2 μH JMR1024XXX SMDJ58A 330 μF / 100 V MLCC, 4.7 μF, 50 V 4.7 μH JMR1048XXX SMDJ120A 330 μF / 100 V MLCC, 2.2 μF, 100 V 6.8 μH www.cieonline.co.uk L2 LDF648075-52UH-3.14A LDF649075-175UH-1.76A LDF649075-419UH-0.78A www.digikey.co.uk Components in Electronics May 2025 21


Table 2: Shown are the recommended component values for the circuits shown in Figure 4. (Table source: XP Power)


Modular and highly integrated DC/DC converters simplify the design of reliable, high-performance power supplies for medical systems. Still, designers must carefully choose a device with IEC 60601-1 certification to ensure it meets the standard’s requirements for operator and patient safety, as well as EMC.


Finally, the medical device must comply with the EMC requirements outlined in IEC 60601-1-2. These requirements aim to improve the immunity of equipment from the many wireless communication devices operating close to life-critical equipment. The secondary objective of the requirements is to provide EMC guidance for equipment used outside of the hospital when there tends to be less control over the EMC environment.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56