Pros and Cons of DC/DC Converter Modules

Designers love a good module, such as popular microcontroller modules like ESP32 and shield form factor modules for Arduino. Closer to the commercial end of the industry, many designs might Implement a DC/DC converter module to provide stable voltage at high power output. Brick form factor modules give great advantages in terms of space expectations and some standard features. For designers who do not have experience building power electronics, but who need high power, a DC/DC converter module in a brick format can be an excellent option.

If you decide to use a DC/DC converter module, what's the downside? These modules might seem like a great option to reduce your design time, but they come with disadvantages such as cost, space requirements, and in some cases availability pressures. Here is everything you need to consider if you decide to use a DC/DC converter module.

Quick Overview of DC/DC Converter Modules

DC/DC converter modules perform the function suggested by their name, they are DC-in/DC-out power supplies, but are supplied in a module form factor. They are off-the-shelf components that require no internal configuration and can be mounted onto a PCB. DC/DC converter modules tend to have standard features and pinouts across manufacturers, so it is often possible to find multiple parts that will satisfy a single operating requirement.

Quarter-brick module from Artesyn (image source)

Selection of a DC/DC converter module demands balancing several design and component factors:

• What is the required power output?
• What is the available space for a module?
• What space is available for supporting components?
• Is isolation needed and what withstand voltage is required?
• Is enough stock available to fulfill a production order?

These modules are available as buck, boost, or buck-boost converters, often with a wide input range. Some of these will output a fixed target voltage with internal feedback, with the goal being to support standard operating voltages used in some industries. For example, 48 V is a common option in order to support telecom equipment or data center equipment.

Based on these characteristics, a DC/DC converter module sounds like a very convenient option. What are some of the pros and cons of these components?

Advantages of DC/DC Converter Modules

A DC/DC converter module has several important advantages, particularly in the areas of standardization and available power output. Of course, another big area is convenience as these components can be purchased off the shelf from a distributor. Take a look at the table below, where the various advantages of a DC/DC converter module are summarized.

Considering the electrical and safety features in these modules, these components are very attractive for designers who are not skilled in designing high power output regulators. Probably the biggest advantage is the convenience of these modules, as they can be purchased off the shelf from many vendors. As through-hole components that are prepackaged and encapsulated, they are very reliable and need no configuration.

Disadvantages of DC/DC Converter Modules

All DC/DC converter modules have some disadvantages. Although they are supplied as off-the-shelf components, they are not really off-the-shelf components; these modules only contain the power regulation and safety circuitry needed for DC/DC conversion. There are additional required components that are not always accounted for when determining form factor. Other issues such as cost and availability at volume are also important to think about as this limits margin for a commercial product.

Given the costs and other disadvantages, it might make more sense to work with a custom module given your product manufacturing volume. For example, consider a typical quarter-brick module with a cost of $100 and expected production volume of 100 units. Just for the cost of the DC/DC converter modules, an experienced power systems engineer could provide a design for a DC/DC converter circuit that satisfies most or all of the specifications listed above.

Of course there are additional costs, such as prototyping and testing, but it illustrates the trade-off between designing a custom circuit and using an off-the-shelf regulator.

Form Factor and Additional Components

Since the big attraction of using a DC/DC converter module is the standardized form factor, let’s dig into this aspect of DC/DC converter modules.

The form factor of many DC/DC converter modules is known as a “brick” format, with the X-Y dimensions of many modules being standardized across vendors. Brick format converters may have differences between various products, even if the X-Y dimensions match across vendors:

• Some products could be encapsulated
• Some products can have a metal baseplate for heat dissipation
• Some modules can expose their components on the bottom side
• Z-axis height may be different in some modules
• Pinouts can be different across modules

Brick format dimensions are readily available online and can be found on a search engine.

Pin functions can also differ across various DC/DC converter modules. For example, a popular configuration in quarter-brick formats is to use a 10-pin format with a standard naming convention, but other pinouts can be found in various modules. An example pinout is shown below.

This image shows the typical dimensions of a quarter-brick format power supply and its pinout/functions. The pinout on this module omits 2 pins which are standard on most DC/DC converters: a Bus pin and a UVLO pin. These additional pins are used for control and stability of the module’s power output.

Pinout and pin functions for the ERM100 DC/DC converter module from Artesyn (source)

Although it’s not stated specifically in the datasheet, the above module isn’t used in isolation. It requires input capacitance and output capacitance which can take up a lot of board space. It can also require an input EMI filter to remove common-mode noise; when the input current is large these input EMI filters will also be very large. Finally, when the input voltage is large, the input capacitors can be exceedingly large. All of this increases the cost and form factor of these modules.

The Verdict

While DC/DC converter modules are very convenient and offer a quick way to provide high power output, they might only be suitable in certain situations or certain types of products. For example, given the high cost of a reasonably advanced off-the-shelf module, money might better be spent designing a custom circuit unless production volume is low.

Before finalizing a module selection, look at the additional capacitance and EMI filtering requirements for the module as these can take up a significant amount of space, especially when the target power output from the module is very high. Once a module has been identified, do a back-of-the-envelope calculation of the area required for all the supporting components to get a true sense of the footprint for a DC/DC converter module circuit.

Alternatives: PMICs or Non-Standard Converter Modules

Aside from a typical brick-format module or a DC/DC converter controller or PMIC, there are alternative modular options for DC/DC converters, including isolated converters, which can run at high power output. An example is the Vicor module shown below, which is a surface-mount modular component with very high power density.

Example PRM48 surface-mount DC/DC converter module from Vicor (source)

These high power output options are great in terms of power density, but higher power density almost always means more heat, even in a highly efficient switching DC/DC converter. In terms of cost, these are mid-range components that are much less expensive than brick modules, but much more expensive than a design built from a set of discretes. If this is the approach you want to take, make sure you are prepared for higher thermal loads than you would expect in a DC/DC converter module.

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