DC/DC Converters for Industrial Applications

Electronic components are designed and manufactured with specific performance characteristics tailored to target applications. Commercial space is the least demanding, with temperatures ranging from 0° C to 70° C and relatively lax reliability expectations. At the other end of the spectrum are military-grade components, with temperatures ranging from -55 °C to 125 °C and extremely strict requirements for radiation tolerance, shock, moisture, and the like. In between these two extremes are a handful of niche application spaces, among which industrial-grade components find their home.

In addition to a -40 °C to 85° C operating temperature range, one of the most important characteristics of industrial components is their voltage tolerance. This is especially important for DC/DC converters, which are required to handle a wide input voltage range and switch it down to the more common 5 V and 3.3 V rails. Typical industrial voltage inputs include 60 V, 48 V, and 24 V. Industrial components also carry specifications for ingress and physical handling. Many are IP67 rated, which specifies a high level of ingress protection against dust and water. Vibration ratings may also specify that a product can be in an environment that moves or shakes and will survive temporary or constant oscillation.

An often overlooked feature of many industrial components is a 10-year supply guarantee. Since these components are likely to be deployed into environments that are difficult to service, the overall product lifecycle is generally quite long. Ensuring a plentiful supply of replacement devices provides a competitive advantage by guaranteeing a long serviceable life.

Figure 1 provides an overview of ROHM DC/DC converters across a range of input and output voltages for industrial applications.

 

Figure 1. ROHM voltage converters for industrial input/output ranges. Image used courtesy of Bodo’s Power Systems [PDF]

 

ROHM Proprietary Technology

ROHM’s DC/DC converters employ two proprietary technologies to achieve best-in-class performance – Nano Pulse Control and QuiCur. Nano Pulse Control is a DC/DC switching technology that offers the industry’s smallest pulse width of only 9 nanoseconds. This is three to four times faster than the nearest competitor, as shown in Figure 2.

 

Figure 2. Reduced switching time enables large voltage conversion ratios. Image used courtesy of Bodo’s Power Systems [PDF]

 

This minuscule pulse width allows the DC/DC converters to handle large input-to-output voltage ratios, which is often required for industrial environments. With Nano Pulse Control, these converters can directly buck a 48 V input rail down to a 1 V output in a single stage. Comparative products, on the other hand, require an intermediate step and two separate conversion ICs.

QuiCur is another technology upon which ROHM's industrial DC/DC converters are built. It is a circuit-level technique that solves several of the main problems plaguing feedback networks for maximum response performance. As shown in Figure 3, this technology relies on introducing two dedicated error amplifiers. In particular, the second stage is critical as it uses a technique whereby its gain is scaled by the overall drive current. The result is a much more flexible frequency response, allowing the designer to choose between optimal stability, minimal undershoot, and reduced physical size.

 

Figure 3. ROHM’s QuiCur circuit topology. Image used courtesy of Bodo’s Power Systems [PDF]

 

With Nano Pulse Control and QuiCur technologies, designers can choose from a broad portfolio of DC/DC converters and LDOs for industrial applications from high voltage/high current to space-constrained and everything in between.

 

High-Voltage, High-Current Solutions

Several common industrial applications start with high-voltage AC mains or battery inputs in the range of 48 V to 60 V. As shown in Figure 4, EV charging stations often include an AC/DC module to provide a 60 V supply from 380 VAC mains. This 60 V rail must be bucked down to 12 V for both the interface circuitry and the high-voltage control circuitry. The BD9Gxxx series of regulators can reliably deliver this 5:1 conversion ratio in a single stage.

 

Figure 4. EV Charging Station. Image used courtesy of Bodo’s Power Systems [PDF]

 

Similarly, electric bicycle batteries based on Lithium chemistries provide DC outputs in the realm of 60 V. The e-Bike’s supporting circuits, as shown in Figure 5, include communication interfaces, high-power gate drivers, and battery management modules, which can draw in excess of 3 A of current at 5 V. The BD9Gxxx series of DC/DC converters can efficiently deliver this type of load current at such a high step-down ratio.

 

Figure 5. eBike Battery Interface. Image used courtesy of Bodo’s Power Systems [PDF]

 

Space-Constrained Solutions

For industrial applications where the input voltage is 24 V or less, but physical space is a premium commodity, Nano Pulse Control and QuiCur technologies offer a reduction in the size of supporting passives required for the DC/DC converters. The BD9Fxxx series is an example and is compared to the traditional BD9Exxx series in Figure 6. The required inductor size and package size yield an area benefit of over 70% while simultaneously offering an increased load current of 67%.

 

Figure 6. Area reduction due to smaller inductors and IC packages. Image used courtesy of Bodo’s Power Systems [PDF]

 

In a similar vein, the improved efficiency of these devices results in less waste heat, in turn reducing the heat sink requirements for reliable operation. As shown in Figure 7, the ROHM part operates nearly 35 degrees Celsius cooler than the competitor when pushing 4 A of current. The required heatsink, PCB stackup, and thermal planes will be less expensive and require less volume.

 

Figure 7. Improved thermal performance eliminates heat sink requirements. Image used courtesy of Bodo’s Power Systems [PDF]

 

When considering QuiCur for improved frequency response, one potential design implication is the reduction of output capacitor size. As shown in Figure 8, when stepping from 0.1 A to 3 A, the ROHM part exhibits one-third of the ripple compared to another switching from a much smaller step. As a result, the designer may choose to reduce the output capacitor size by 70% for the same performance and save in both space and cost.

 

Figure 8. Fast transient response reduces output capacitor requirements. Image used courtesy of Bodo’s Power Systems [PDF]

 

DC/DC Converters for Industrial Applications Summary

Industrial applications present a unique set of environmental constraints commercial-grade electronics components cannot survive. Foremost among these are high input voltage and high temperature. ROHM’s proprietary Nano Pulse Control and QuiCur technologies are at the heart of a suite of DC/DC converter products that thrive in these environments. They provide large input-to-output ratios, high-performance frequency response, and an overall reduction in physical volume and supporting componentry. As such, these devices find themselves at the front end of many industrial systems and should be at the top of the designer’s toolbox when tackling these challenging problems.

 

This article originally appeared in Bodo’s Power Systems [PDF] magazine

Featured image used courtesy of Adobe Stock