Powering the Future of 48-V Robotics

Article By : Ali Husain

Many modern robotics applications use a 48-V bus to transport power around the system. Compared with a typical 12-V bus, 48 V offers 1/16 of the losses or allows thinner and lighter cables to be used...

Industrial robots are an important element of the Fourth Industrial Revolution, and as these devices become connected to systems and remote sensors, they form a significant subsection of the internet of things: the industrial IoT (IIoT).

According to the International Federation of Robotics, or IFR (www.ifr.org), there were almost 2.5 million industrial robots deployed in 2018, and this number is growing at more than 400,000 units annually. The industrial, automotive, and electrical/electronic sectors account for more than half of total deployments, with the metal and machinery, plastics and chemical, and food and beverage industries being significant users as well. Approximately 75% of all industrial robots are deployed in China, Japan, the United States, South Korea, and Germany.The rapid adoption of robots is not confined to the industrial sector; 250,000 professional service robots were deployed by 2018, a total that represents a staggering increase of more than 60% over the prior year. Two out of every five service robots deployed are classified as autonomous guided vehicles (AGVs) used primarily in logistics and manufacturing. The personal- and domestic-robot market grew similarly (60%) and now comprises about 16.3 million units, used for tasks ranging from vacuuming to education and research.

48 V and robotics

Designers are adopting 48-V power sources for a range of applications, in part because 48 V is the highest safe voltage in common use. Solutions based on 48 V reduce the need for system protections compared with mains-powered devices and reduce the size of conductors compared with 12-V–powered products, thereby reducing system weight and cost as well as power losses. Motors that are powered directly by 48 V are also generally smaller, allowing for smaller and lighter robotic joints and thereby increasing machine efficiency, dexterity, and reliability while reducing weight and cost. This opens up more potential opportunities for robot use to improve the automation of processes in all industries.

Modern applications in which 48-V power is increasingly popular include automotive, where it is rapidly becoming preferred over 12 V for many on-board devices, and cloud computing, where 48-V power distribution is used for server backplanes, cooling fans, and other telecom-related applications. This prevalence means that devices and subsystems for 48-V power are commonly available, increasing the range of options available to designers and lowering costs through economies of scale.

Robots are fairly complex systems. Depending upon the application and functionality, they will comprise a number of functional elements, including connectivity, image sensing, position sensing, and motor control. There are also power subsystems to consider, including AC/DC conversion, battery management, DC/DC conversion, multiphase converters, point-of-load (PoL) conversion, linear regulation, and motor drivers. Each of these areas requires an efficient solution for the robot to operate as the designer intended.

Figure 1: High-level block diagram (including power system) of a typical robot (Image: ON Semiconductor)

If we were to look at similar functional block diagrams for automotive or cloud computing systems, we would find a significant number of similarities with the robot block diagram. This presents opportunities to cross-pollinate power solutions from other applications to robotics. As an example, electronic fuses are used extensively in cloud computing to allow for hot-swapping of storage media and cooling devices such as fans. However, in a robotics application, the same e-fuses could be used to introduce modularity, thereby permitting functional blocks (such as tool pieces) to be exchanged by the robot itself — even in the middle of an operation, depending upon the task at hand.

Delivering power solutions for 48-V robotics

Many modern robotics applications use a 48-V bus to transport power around the system. Compared with a typical 12-V bus, 48 V offers 1/16 of the losses or allows thinner and lighter cables to be used. In fixed robot installations, the 48 V will be generated by a mains-fed power supply that will incorporate a power-factor–corrected (PFC) front end. Mobile robots, such as drones and care assistants, will have an on-board battery that is replenished periodically from a mains-powered adapter.

Few semiconductors are able to work directly from 48 V, generally requiring voltages of 5 V down to the sub-volt level. The non-isolated PoL converter plays an important role here, converting a higher voltage to the level that the IC requires. In some cases, an intermediate bus voltage (typically 12 V) would be created by using an intermediate bus converter (IBC) that is loosely regulated with the PoL converter converting the 12 V to the IC supply voltage. Increasingly, single-stage conversion is preferred, and many PoL converters are now available to convert directly from the 48-V rail to the IC supply voltage.

As with every power solution, the power architecture for a robotics application is required to be efficient and reliable, as well as offer high levels of power density so that the robot can be small and nimble enough to perform its function(s) well. Key to achieving this is to select the right semiconductors to form the various power functions within the robot.

Semiconductor solutions for robotic power applications

ON Semiconductor has applied its expertise and resources to offer a wide range of devices and power products that let designers create high-performance power solutions for robotics applications.

One of the most common devices used in almost all power solutions is the MOSFET. ON Semiconductor’s extensive range includes superjunction MOSFETs with multiple versions for different switching types and applications. The company’s FAST devices offer high efficiency in hard-switching topologies, while its Easy Drive devices are suitable for both hard- and soft-switching applications, where they ensure low electromagnetic interference (EMI) and reduced voltage spikes.

Complementing the MOSFET offering is a wide range of high-voltage gate drivers that allow a microcontroller or other logic circuit to control MOSFETs directly. Depending on the circuit configuration, a simple non-isolated driver (such as ON Semiconductor’s NCD570x series) may be used, or a more sophisticated, isolated solution or high- and low-side driver may be needed.

Highly integrated solutions such as intelligent power modules and automotive power modules bring a number of benefits. Typically, these will integrate multiple MOSFETs for multi-phase motor driving along with the necessary driver devices. These modules offer better thermal performance than discrete solutions because all devices are mounted on the same substrate. They are also able to handle higher current levels while improving EMI and providing a solution that is smaller and lighter than discrete equivalents.

Alongside these solutions, ON Semiconductor offers a complete portfolio for robotic power applications including electronic fuses, PFC ICs, rectifiers, current sensors, and switching devices for providing auxiliary power rails. This portfolio is complemented by the industry’s lowest-power Bluetooth module for communications and a wide range of image sensors for advanced machine vision.

This article was first published on EE Times Europe

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