What are the key considerations in the design of a medical power supply?
The term ‘medical-grade’ is used for a wide variety of power supplies that may look no different to their commercial-grade counterparts.
However, medical-grade power supplies have been specially designed to meet the IEC60601-1 medical equipment safety standard, which influences the internal power supply design.
Safety is not the only factor that distinguishes medical-grade power supplies from commercial models. Medical equipment typically requires longer design cycles than other types of equipment and medical equipment designers often require enhanced design support from the power supply vendor. In addition, medical equipment usually has greater life expectancy than other equipment. Therefore, power supplies designated as medical-grade generally need to be supported by the power supply vendor for many years.
Beyond the volts, amps and safety approval considerations that are common to the selection of almost any power supply for OEM equipment, here are some design considerations that can make it easier for customers to select the right medical power supply:
- Define and specify the power requirements as early in the design process as possible
- Use a standard off-the-shelf medical power supply if possible and consider configurable solutions before jumping straight to the custom design option
- Evaluate your potential suppliers’ quality system
- Consider your second source strategy
Specifying a Medical Power Supply
Here is a checklist of considerations to help you when specifying a medical power supply.
Electrical Requirements
- Input/output requirements DC-DC or AC-DC
- Class I (3 wire AC input) or Class II (2 wire AC input)
- Number of outputs
- Voltage and current of each output
- Output wattage of each output W = V x A
- Calculate total power supply wattage by adding all the outputs’ wattage
- EMC/EMI (radiated and conducted)
- Efficiency
- Holdup time
- Control and monitoring functions
Mechanical Requirements
- Physical SizeL x W x H, weight
- Mounting requirements
- Cooling, forced air, convection or conduction
- Thermal considerations, airflow, temp. rise
- Shock and vibration requirements
- Electrical connections, input and output of power supplies
- Type of mating connectors, wiring harness, etc.
- Acoustics, especially in noise sensitive applications
- Reliability
- MTBF, Life and QAV
Environmental/Safety/Regulations
- Hospital/clinic/in-home/portable/fixed
- Airborne/ship/ambulance
- Ambient temp requirements
- Altitude
- Medical safeties
- 60601-1
- Patient contact/vicinity (MOPP/MOOP)
- RoHS2 (Removal of Hazardous Substances)
- WEEE (recycling)
- REACH
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