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Don’t Forget Current Sharing When Connecting Multiple Power Supplies

For 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.

Don’t Forget Current Sharing When Connecting Multiple Power Supplies

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.