With the popularity of switching power supply technology, linear power supplies don't get the attention they deserve. But linear power supplies outperform switching units in clean-power applications that need minimal ripple current and low noise. Watch our new video to learn more.
Want to make sure that the medical equipment you design will do more good than harm? Then pay attention to the power supplies you use. Many industrial power supplies simply do not comply with the safety standards that govern diagnostic, monitoring and treatment equipment. Watch our new video to learn all about linear and switching power supplies that do meet global standards for patient safety.
With the advent of highly efficient switching-mode power supplies, linear power supplies are often thought of as old-fashioned and not very useful except in a few specific applications. Nothing could be further from the truth. In fact, modern versions of linear power supplies are making their way into a wide range of industries and applications that demand clean power with very little ripple and low noise (EMI and RFI).
Let’s take a quick look at the major differences between these two styles as well as a few applications where linear power supplies really shine:
Switching power supply advantages: For higher efficiency, a smaller form factor and lighter weight, switching power supplies are the clear winner. However, this higher efficiency and lower heat dissipation comes at a cost. Not only are they more expensive than linear versions, they’re also more complex and can cause electrical noise issues. Even so, their high performance, small footprint, and proven reliability are hard to beat compared to their linear counterparts.
Linear power supply advantages: When low common mode noise is a must, making the tradeoff between the higher efficiency of switching power supplies and lower noise of linear styles makes sense. Switching power supplies just can’t offer low enough ripple for certain applications. A simpler design and lower part count also makes mean time between failures another key advantage of linear designs over the more complicated switching-mode construction.
Key applications for linear power supplies: Simply stated, linear power supplies are an ideal choice when output noise must be kept to a minimum. Applications such as high-end audio equipment, lighting designs such as LEDs, sophisticated sensors, and redundant power for power generation scenarios are all prime candidates for linear power supplies due to their minimal noise output and low ripple. Medical equipment also requires linear power supplies as well, though there are only a few products on the market certified to meet industry standards for patient and operator protection. The key is choosing the right power supply for the type of load in question, and balancing efficiency needs with noise requirements.
If you’re in the market for a power supply, your first step is figuring out what’s most relevant to your application: How important is low noise? What kind of package do you need? Are there any MOPP or MOOP requirements?
In many applications—especially within the medical industry—some things just can’t be overlooked. And to make sure you pick a power supply with all the necessary specs, you’ll oftentimes have to settle on a power supply with a higher wattage. Using a power supply with more wattage than the device requires can both drive up prices and lower efficiency.
For medical applications that need a low wattage power supply that still meets all its necessary requirements, our 65-watt series of universal input power supplies has plenty to offer.
What MUI65 offers. The MUI65 series offers 92 percent high efficiency and 2 MOPP isolation for patient protection, all in a compact package of 2.00 x 3.00 x 1.16 inches. It delivers a low leakage current under 75µA, 2000 VAC input to output and an operating temperature range from -25 to 80°C.
These power supplies also meet the following safety standards: UL, CE and ANSI/AAMI ES60601-1, EN60601-1 and IEC60601-1 Third Edition, as well as RoHS compliance to 2011/65/EU. Other features include:
- An operating altitude of 500 M
- Protection type class 1 and class 2
- Output voltage adjustable in single output models
- Low standby consumption
Package options. One major benefit of our MUI65 is its many packaging options. Here’s a look at each of them, along with closer look at what they can provide for your application:
- Open type: When applying a power supply in a closed system, room or rack, an open type is the best package option for saving space and lowering costs.
- U chassis type: U chassis mounts have a three-sided metal case seal with no top. Sometimes, engineers add a fan to the top to keep temperatures down.
- Enclosed type: An enclosed package is sealed with a metal case on four-sides for increased protection. It can be either independently or externally mounted.
- Din rail type: Din rail mounts are attached to the circuit by wires, allowing you to move it from one spot to another in the case of re-design.
- Screw terminal: Screw terminal packages are easy for application hook-up since you don’t have to specially design the board to accept the pins—you just bolt and wire it.
You know the different types of power supplies: Linear models are known for their reliability, transient response and low ripple and noise, while switch-mode units are compact with high efficiency levels and wide input voltage ranges.
Switch-mode power supplies usually have ample efficiency, but their unpredictable noise can be problematic. For medical applications, the goal is to find a power supply that exhibits both low noise and high efficiency—a rare feat. It’s also important to choose one that meets both patient and operator safety requirements.
Hemedex, a maker of blood flow monitors, was able to strike this balance in its Bowman Perfusion Monitor. Read our latest case study to find out how.Download the Case Study
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