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Don’t Forget Current Sharing When Connecting Multiple Power Supplies

Don’t Forget Current Sharing When Connecting Multiple Power SuppliesFor many medical devices, a switch mode power supply (SMPS) will be ideal for the design. After all, an SMPS provides excellent efficiency and power density for its typically small size. However, there are some instances where it may be desirable to use more than one switching power supply in a design. This blog post will explain why connecting power supplies in parallel makes sense, and it will show why including a means of current sharing in your design is important in these situations.

When To Consider Multiple Power Supplies

There are typically three reasons to use more than one SMPS in a medical device design:

  • The load requires more current than a single SMPS can provide.
  • Power supply reliability is critical, as is often the case with medical devices. Multiple power supplies provide the necessary redundancy for the application.
  • Longer power supply lifetimes, thanks to better heat distribution.

Keep in mind that using multiple SMPSs involves challenges, and it is not always a straightforward process. For example, simply connecting power supplies in parallel does not necessarily mean that the load current will be distributed equally. Uneven distribution of the load current may stress power supplies or create thermal issues, resulting in premature power supply failure. In order to configure multiple power supplies in parallel, a controlling element is needed to ensure that current is shared equally.

As you consider using multiple SMPSs in your medical device design, be sure to understand the different methods of current sharing and select the right one for your application. Also, when selecting your SMPS, look for a power supply designed with current sharing in mind. Power supplies with built-in current sharing circuitry enable parallel connections with equal distribution of load currents when used with appropriate external components.

We offer a variety of switching power supplies with optional current sharing. For example, most models of the recently introduced PFMUIE500 Series of medical switching power supplies can be specified with a current sharing function, and they come in a 5.5 by 3.25 by 2.42-inch enclosed package to economize space in designs that call for parallel connections. In addition to their 500 watts of output power, the PFMUIE500 Series also features:

  • 4,000V AC input to output 2MOPP insulation for patient safety.
  • Remote ON/OFF function.
  • Standby of 5V at 1A.
  • Up to 92 percent efficiency.
  • PFC function of >0.94.

Built-in Current Sharing Simplifies Designs and Enhances Reliability

When an application requires parallel power supplies, configuring a system with equal current sharing can be challenging. There are many factors and current sharing methods to consider, so be sure to work with your power supply manufacturer to make sure your system is configured correctly and with the proper components. Switching power supplies with built-in current sharing, such as the Polytron Devices PFMUIE500 Series, can help reduce the uncertainty and complexity involved with implementing multiple power supplies in your medical device design.

Find out more about our PFMUIE500 Series medical power supplies.

Learn How Power Supplies With PFC Make Greater Use of Grid Power

Learn How Power Supplies With PFC Make Greater Use of Grid Power

If you’re integrating a switch mode power supply (SMPS) into a system, you expect good power efficiency. You also have to be sure you’re getting the most useful energy when drawing power from the AC main. To get the most of your AC power draw, you must also consider the power factor during your SMPS selection. Let’s discuss some of the basics of power factor and what you should look for in a switch mode power supply.

Power Factor Basics

As switch mode power supplies draw power from the grid, not all of that power can be used. The SMPS typically draws the AC input current in short, high-magnitude pulses. As a result, the current is out of phase with the voltage. Because of the variance, some of the main energy is displaced and unavailable for useful work. This condition is known as power factor — a ratio of the supply’s working power compared to its apparent power. Power factor is expressed as a decimal between 0 and 1.

Without maximum working power, the system must draw more power and incur the associated costs. Poor power factor can also create harmonic distortion that can damage equipment in the circuit. To avoid these situations, power supply manufacturers employ power factor correction (PFC) techniques to bring the supply’s power factor as close to 1, or unity, as possible. For low-power supplies, PFC typically involves smoothing out the short pulses using passive components to create a low-pass filter. Higher-power supplies use control circuitry or a regulator to harmonize the input voltage and current. For most applications, SMPS that achieve a power factor of 0.9 or higher are ideal.

Our new UIA700 Series 700-watt switching power supply is one such example. It comes with a power factor figure of greater than 0.9, making it appropriate for a wide range of industrial equipment. It accepts a wide 90 to 264V AC input for use globally, and its small size of 6.7 by 3.66 by 1.61 inches makes it ideal for space-constrained applications. And, you don’t have to choose between a high power factor and high efficiency, thanks to the UIA700’s 92-percent efficiency rating.

Additional features and specifications include:

  • A remote ON/OFF function for energy savings.
  • Standby: 5V at 1A.
  • Chassis mount with terminal strip.
  • UL/IEC/EN 62368 approval.

When specifying a SMPS, keep in mind that domestic and international regions have regulations that define local power factor or harmonics requirements.

Optimize Power and Space

Switch mode power supplies with a PFC function make the best use of the main power, and those with a power factor of 0.9 or better are preferred for most applications. Our UIA700 Series switching power supply combines a high power factor, high efficiency and small size to achieve optimal AC power for a broad range of industrial applications.

For more information about Daburn Electronics’ Polytron Devices UIA700 Series switching power supply, visit our product page.

Look For These Features To Avoid Damaging Your Power Supply

Look For These Features To Avoid Damaging Your Power Supply

Many of today’s power components come equipped with built-in protection features that will turn the device off when fault conditions occur. They can also include remote status signals that alert users to certain operating conditions or functions that may require adjustment or regulation. This blog post provides a summary of some of the most common built-in protections and status signals found in power components:

  • Overtemperature Protection. When internal components heat a DC/DC converter beyond a set temperature, this control shuts the converter down to protect both the converter and downstream components against failure.
  • Short Circuit Protection. This feature monitors the output power rails and shuts off the output power when a short circuit occurs.
  • Power Fail. A signal that indicates a loss of main input power or a drop in voltage below a threshold where the power supply will not provide adequate power. The converter will continue to operate for a few milliseconds to store data or to allow the system’s backup power to take over before shutdown.
  • Power Good. As a system powers up, the Power Good feature will prevent the system from operating until a set output voltage is achieved. This thwarts any potential damage that can happen when running at an improper voltage.
  • Inhibit and Enable. There may be times when the user needs to take action to turn the output voltage on or off without using a relay. Specifically, Inhibit induces the user to turn off the output voltage, while Enable means the user must turn on the output voltage.
  • Remote ON/OFF. Many devices require the DC/DC converter to be enabled or disabled intermittently, such as components that run on standby power. This function can also turn the converter off to protect against damaging inrush currents. The way you implement remote ON/OFF will vary depending on the converter and its logic. This blog post provides more information about remote ON/OFF including the types of logic involved.

AC/DC Power Supplies Offer Monitoring and Built-in Protection Features

You can find some of these monitoring and protection features in our new UIA600 AC/DC switching power supply. This 600-W unit offers input voltage ranges of 90 to 264V AC or 120 to 370V DC. It also includes a 12V DC output voltage, power factor of >0.95 and efficiency up to 93 percent. The power supply’s Power Good output voltage range is from 3.7 to ~7.5V, and the device turns off from 0 to ~1V output voltage. It also offers remote control protection, configured as +RC / -RC: Power ON=open; Power OFF=short.

Additional built-in safeguards include overtemperature, overload and short circuit protection, and each activates the auto-recovery feature when the condition is resolved. The UIA600 also features a current share function to provide more current to power a load while using a constant voltage.

Get Started Today

To make sure your power supply doesn’t suffer harm from adverse conditions, remember to look over the manufacturer’s datasheet for built-in protections and status signals. With the right adjustments and regulation, both the power supply and downstream components can avoid damage. Our UIA600 AC/DC switching power supply offers many of these protective features, along with a current-sharing function for parallel connections. Our engineers are ready to assist you in selecting the best switching power supply for your application.

For more information about Daburn Electronics’ Polytron Devices UIA600 AC/DC switching power supplies, download our datasheet.

Protect Your SMD Power Product From Damaging Moisture

Protect Your SMD Power Product From Damaging Moisture

When it comes to mounting components to circuit boards, surface mount technology saves board space and assembly time. Advantages include higher component density, resulting in smaller circuits and faster circuit speeds, plus shock and vibration resistance, and low noise. Because of these and other benefits, surface mount-packaged (SMD) components are a logical choice for automated assembly. However moisture can cause a “popcorn effect” during solder reflow.

In order to help OEMs take proper care when handling and storing moisture-sensitive devices, the Association Connecting Electronic Industries created the IPC-M-109 Moisture-sensitive Component Standards and Guideline Manual. Among its seven documents, IPC-M-109 defines moisture sensitivity levels (MSLs), with each numerical level corresponding to the part’s risk of incurring the popcorn effect: Level 1 is the lowest risk, and Level 6 indicates the highest risk. Each level determines how long a moisture-sensitive device can be exposed to ambient room conditions (≤30°C and 85 percent relative humidity at Level 1; all other levels: ≤30°C and 60 percent relative humidity).

Find out the Product’s Floor Life

Many vendors list MSL information under the “Environmental” section of the datasheet. For example, the datasheet for Daburn Electronics' Polytron Devices MTWA4 Series of 3.5-watt DC-DC converters for medical applications indicates they are available in a 0.95 x 0.57 x 0.40-inch miniature SMD package and carry an MSL level of 2. That means it can be stored, mounted and reflowed within one year of “floor life” outside of a moisture barrier bag at less than or equal to 30°C and 60 percent relative humidity. Should the part exceed its floor life, that moisture will have to be baked out, slowly, before assembly. In addition to their miniature size, the MTWA4 converters provide 5,000 Vac input to output 2 MOPP isolation and remote ON/OFF. Their voltage input range (4.5 to 12V DC) makes them well-suited for portable devices. The MTWA4 Series of SMD-packaged DC-DC converters is well-suited for automated assembly and can satisfy various input and output requirements.

When using a surface mount component in your design, manufacturability and reliability depend on proper storage. Be sure to check the manufacturer’s datasheet for the part’s numerical moisture sensitivity level (MSL) in order to determine its floor life, and to refer to IPC J-STD-020 and J-STD-033 for other storage and handling procedures based on the MSL. The better informed you are about moisture levels according to JEDEC/IPC standards, you’ll have more certainty that your part will perform as intended.

To learn more, get in touch with our technical staff.

Save Time and Effort With Custom Linear AC/DC Power Supplies

Save Time and Effort With Custom Linear AC/DC Power Supplies

If you need a custom AC/DC power supply that offers low noise and ripple, simplicity, reliability and economy, chances are the ever-popular switching power supply won’t satisfy all your needs — especially when it comes to low noise. Thankfully, there are still power supply manufacturers that can provide an AC/DC linear power supply that can satisfy requirements for industrial, medical and other critical low noise applications.

Manufacturers typically focus their efforts on switching power supplies, so finding a vendor that offers custom linear supplies can be a challenge. The Polytron Devices Division of Daburn Electronics is one of a few suppliers that are committed to customizing linear power supplies. When specifying a custom AC/DC linear power supply, these are the factors to look for in a vendor:

  • A solid legacy of producing AC/DC linear power supplies
  • A commitment to AC/DC linear power supplies
  • The ability to satisfy high power requirements
  • The ability to provide many types of modifications to linear power supplies
  • Engineering expertise
  • Volume advantages to keep costs low

How We Can Tailor a Linear Supply To Your Needs

As other manufacturers de-emphasize or even phase out linear power supplies, we're building on the legacy of our P3 and P5 Series low noise, precision linear power supplies — continuously available since 1969 — by expanding customization capabilities and upgrading our original designs for medical applications.

At Polytron Devices, we're well-known for low-noise medical and industrial linear power supplies. We can satisfy a wide range of custom needs such as:

  • Providing multiple output voltages in a single model
  • Adding programmability or ON/OFF switches
  • Adding a variety of types such as open frame, desktop and wall plug-in models, in addition to enclosed units for harsh environments

We have also upgraded our power capability. Our previous offering had a range of 1 to 30 watts, maximum, while our latest supplies now cover 1 to 450 watts, maximum. Our engineering staff is available to assist you throughout the process. Simply send us your tech specs and we’ll suggest solutions for your unique requirements, create evaluation samples, safety-test the unit and help ensure regulatory approvals for IT equipment and medical equipment.

We’ll also work to get your custom unit to you when you need it while keeping costs in check. For example, transformers are the most expensive part of the linear power supply. But thanks to our strong relationships with transformer manufacturers, we have access to large quantities of transformers to get them fast and cost-effectively. We also accommodate blanket orders so you can lock in quantity pricing while receiving your product as you need it.


Saving You Time and Effort

Because most power supply manufacturers focus on switching-type supplies, specifying a custom linear AC/DC power supply has become a challenge for designers. We can meet your linear power supply needs with custom units tailored to your application. When you work with our engineers and sales support team, you’ll save time, effort and money so you can get your product to market faster.

For more information about our custom linear AC/DC power supplies, contact us.

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