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The MEAN WELL MPM and IRM series of AC/DC power supplies. (Image courtesy of MEAN WELL.)

For applications that have limited space and require high efficiency, onboard power supplies may be your best bet. In this article, we’ll take a look at the advantages of onboard power supplies and check out a few examples.

Onboard Power Supplies

Onboard power supplies are designed to fit effortlessly onto your system’s printed circuit board (PCB). Even so, onboard power supplies still provide all the standard features, such as full protection, Class II isolation, high efficiency and free air convection cooling. They can be manufactured in an open frame or with an encapsulated design.

Onboard power supplies are suitable for many applications, such as medical devices. Medical applications have strict regulation requirements, and tend towards miniature devices where compactness is critical. Onboard power supplies are also a good match for IT equipment, general electronics, industrial use and more.

An example of onboard power supplies for medical use is the MEAN WELL MPM series. This series encompasses power levels from 5 to 90W to suit various applications and load requirments. The MPM series is significantly smaller in size and provides a wider operation temperature range compared to MEAN WELL’s previous generation.

Understanding Medical-Grade Power Supplies

MEAN WELL’s MPM series are medical-grade onboard power supplies. This is ensured by reinforced isolation with two means of patient protection (2x MOPP) and low leakage, which provides an additional level of safety.

At least one MOPP is required if patients could come into contact with a medical device, such as ultrasound scanners, MRI machines, defibrillators and dialysis machines. The highest level of protection specified in the standard requires at least 2x MOPPs. This means 4000VAC isolation voltage, 8mm/5mm creepage/clearance and double insulation.

Low leakage currents provide an additional protection for the patient. This is very important because currents as low as 40mA can be fatal for healthy people, and ill patients can be fatally injured by even lower currents. The MPM power supply design ensures that the touch current does not exceed 80µA at 264VAC.

Medical power supplies require advanced safety standards, lower EMI (electromagnetic interference) and EMC (elecotrmagnetic compatibility) compliance. These are requirements for medical power supplies to comply with medical safety standards IEC/EN60601-1 and ANSI/AAMI ES60601-1 3rd version, which are the necessary standards for medical use in a hospital or residential home. The 3rd version of the standard is focused on the safety of personnel and patients with access to the medical electrical equipment.

These standard guidelines are more rigorous than those for other commercial or industrial appliances. Typical medical applications include medical testing apparatus, portable medical devices and medical equipment requiring extremely low standby power consumption.

A syringe pump, a typical medical application of the MPM onboard power supply. (Image courtesy of MEAN WELL.)

For medical applications where the patient’s life depends on a medical device, any malfunctions caused by electromagnetic or radio interference must be avoided. The final device, including the power supply, must be confirmed to meet EMC requirements. The below table reveals the safety and EMC characteristics of the MPM series.

Safety and EMC characterstics of MEAN WELL MPM power supply. (Image courtesy of MEAN WELL.)

The MEAN WELL IRM Series

Another example of onboard power supplies is the MEAN WELL IRM series of miniature AC-DC module-type power supplies, which can be soldered onto the PCBs of various electronic instruments. The IRM series offers both PCB mount and screw terminal designs.

The MEAN WELL IRM power supply PCB mount model. (Image courtesy of MEAN WELL.)

The MEAN WELL IRM power supply screw terminal model. (Image courtesy of MEAN WELL.)

The MEAN WELL IRM green power modules include the 90W IRM-90 series that can meet higher wattage demands. These power supplies can also be directly mounted and soldered onto the PCB. Additionally, the IRM-90-xST screw terminal type can offer alternative mounting and wiring options. These power supplies are mounted in a plastic case. The fully-potted silicone enhances heat dissipation, meets anti-vibration demands up to 5G and provides resistance to dust and moisture.

The MEAN WELL IRM-90. Left: PCB mounting style model. Right: screw terminal style model. (Image courtesy of MEAN WELL.)

The MEAN WELL IRM series of onboard power supplies targets applications including industrial electrical equipment, mechanical equipment, factory automation equipment, handheld electronic devices, internet of things (IoT) systems and communication equipment.

No-Load Power Consumption

Applications that operate on low duty cycles—such as alarm systems, process controls and building automation systems—usually waste energy between active uses. Power supply manufacturers have designed systems to decrease power consumption during these no-load conditions and run the systems efficiently in active mode. These power supplies provide low no-load power consumption and the ability to quickly return to full output power when it's needed.

The MEAN WELL MPM series of onboard power supplies provides very low no-load power consumption below 0.075W. The IRM series have less than 0.1W. These power supplies must have advanced circuit dynamics to switch from low no-load power to normal operating power.

The MEAN WELL MPM 20-12 onboard power supply. (Image courtesy of MEAN WELL.)

The Importance of Supply Efficiency

Power efficiency is the percentage ratio of total output power to input power. It represents the amount of input power that is available as power supply output and reveals how much power is lost—mostly as heat, which needs to be dissipated properly to avoid damaging the unit. It is never possible to achieve a power supply efficiency of 100 percent, but it’s an admirable target.

Power supply efficiency adds up. According to the National Resources Defense Council (NRDC), increasing the efficiency of external power supplies by 15 – 20 percent could save 32 billion kWh per year, cutting the annual national energy bill by $2B and reducing the carbon dioxide emission by 24 million tons per year.

In 2014, the US Department of Energy (DOE) published the stringent Level VI energy efficiency standard, which calls for significantly reduced no-load power consumption and increased efficiency limits during active operation. The no-load power consumption was reduced almost 3x from the previous standard, setting the limits to 0.1W for external power supplies below 49W and 0.21W for power supplies in the range from 49W to 250W. The efficiency limits were also increased to 81.9 percent.

The MEAN WELL MPM power supplies offer up to 87 percent efficiency, and the IRM power supplies up to 93 percent.

Get On Board

Though simple in purpose, the design considerations of power supplies are numerous. Whether you’re looking for medical-grade supplies, high power options, or just want to ensure high efficiency, onboard power supplies are up to the task.

To learn more about the MEAN WELL MPM series of medical-grade onboard power supplies, click here. For more information on the MEAN WELL IRM onboard power supplies, click here.