By Thong “Anthony” Huynh, Principal Member of the Technical Staff, and John Woodward, Executive Business Manager; Industrial Power, Maxim Integrated
Miniaturisation is a trend that is not just limited to consumer electronic products like wearables and portable speakers. In application areas such as transportation, buildings and factories, the equipment providing the intelligence and autonomous functions is getting smaller and sleeker. For example, in the transportation sector, fleet management devices that track vehicle location and maintenance schedules need to be compact enough to fit under a dashboard. In smart buildings and homes, processors and connectivity interfaces are integrated into tiny controllers, sensors and actuators to help manage temperature, security and lighting. And in automated factories, as intelligence moves to the edge, this creates demand for increasingly smaller sensors and actuators that enable equipment to make decisions and adapt dynamically to changing manufacturing requirements. On the consumer side, the move to USB-C for single-cable, bi-directional data transmission and power delivery continues the pressure toward miniaturisation in this space, as well as on the industrial and medical devices that are now adopting this communication protocol.
As a wide range of equipment and devices shrink in size, the power supplies for these applications need to follow suit. When it comes to power supplies, size is an important consideration in a number of industrial applications. Automation in sectors including transportation, buildings and factories is driving a need for increased miniaturisation and efficiency in all of the underlying components. Indeed, applications ranging from devices using USB-C to drones, robots, currency counters and GPS trackers all face similar demands. Despite being space-constrained, the power supply designs for these applications often need to support demand for more power.
The challenge, of course, lies in balancing the size requirements with the power conversion efficiency and thermal management challenges.
For any company managing a fleet of vehicles (Figure 1), vehicle tracking devices provide a wealth of data that helps the organisation optimise fleet efficiency, track vehicle maintenance schedules and keep tabs on vehicle location. Installed under the vehicle dashboard, these trackers are generally powered by the vehicle’s battery (12V for cars, 24V for many trucks), with a rechargeable backup battery in place if needed.
The traditional architecture for an asset-tracking device’s power circuit consists of linear regulators, or LDOs. These power ICs convert protected voltage from the front-end electronics into lower voltages that power the digital logic and analog ICs in the tracker. The problem with LDOs is, their power dissipation is high when they’re used directly from the main battery voltage. Considering the placement of these trackers under the dashboard, low heat dissipation is desired. A compact, more efficient power supply solution would provide a better alternative.
Trackers used in fleet management need to be small and have low heat dissipation
Self-control in buildings and smart home
Thanks to smart control and automation technologies, building managers can now turn lights on and off, change the temperature or check their security-camera footage remotely. In fact, the building might even be smart enough to manage all these functions on its own, providing adjustments in real time. The system architecture for building automation consists of:
- A management layer that operates and controls the building from a central location via network protocols such as BACnet and Modbus;
- A control layer that handles the building’s equipment control at the hardware level via protocols such as KNX and LonWorks;
- A field layer where intelligent sensors and actuators collect data and perform functions, such as adjusting the building’s lighting based on the amount of sunlight available at a given time of day.
The sensors and actuators communicate with the control centre via wired or wireless gateways. The controller processes inputs received from field sensors to drive the proper actuators. Both the sensors and the actuators have processors inside that enable them to make simple decisions locally, reducing latency. Considering the intelligence provided by the network of sensors and actuators inside a smart building, one can picture the amount of processors and connectivity interfaces needed. Furthermore, one can see how this places power and size constraints on the system hardware: the same chassis must be able to accommodate all these electronic components, whilst the smaller resulting PCB size demands efficient thermal dissipation. Heatsinks for thermal management are out of the question here given the board space constraints, as are fans for forced airflow because of the sealed enclosures. Building automation systems call for a small, highly-efficient power supply.
Smart home applications place similar demands on their power supplies. Homeowners can control everything from garage doors to sprinkler systems, lighting, temperature and security from apps; see Figure 2. Like their commercial building counterparts, these smart-home applications also rely on tiny smart sensors whose power supplies need high voltages with low heat dissipation.
Robotic and other automated equipment on manufacturing lines across the world increase productivity and minimise downtime. Smart sensors and encoders are integral to bringing intelligence to the edge of the smart factory, enabling production lines to quickly adapt to changing manufacturing requirements, identifying problem spots in real time and streamlining processes, including maintenance schedules. Smart sensors derive their intelligence from IO-Link compliance, full field configurability and real-time diagnostics. Their small size enables them to be ubiquitous around the factory floor. At odds with their trend toward miniaturisation is the increased heat dissipation that results from providing smart features. Powering these sensors calls for addressing not only the size and heat considerations, but also their accuracy. For this, designers must maintain low noise and high power supply rejection ratio (PSRR).
By electronically monitoring the position of a rotating shaft, absolute encoders enable precise position control in applications such as packaging, robotics, pick-and-place and rotary table positioning. Incremental optical encoders monitor speed and direction and, with additional hardware and software, position. Their power supply challenges are similar to those of sensors: balancing heat, size, noise and PSRR. Also, given the harsh environment of a factory, both sensors and encoders (and their underlying components) must be able to perform reliably in the event of vibration, shock and drops.
Universal cable promise
The USB-C protocol brings to life the promises of a versatile, universal cable for charging devices, transferring data and connecting devices to peripherals. USB-C supports up to 3A at 5V and works well for many applications that need less than 15W power, supporting data transfer rates to 10Gbps. USB-C Power Delivery supports power delivery 100W (5A at 20V). The USB-C port is just 8.4mm x 2.6mm. With the single wire involved, a real-time negotiation must happen between systems to enable a power delivery scheme after a USB-C plug is inserted into a device. Transitioning from the previous USB 2.0 architecture requires accommodating the reversible connector for USB-C, along with higher power levels. USB-C adoption is spreading beyond consumer devices into application areas including medical and industrial. For example, we’re starting to see the communications protocol being used in medical imaging sensors and machine vision cameras. Traditionally, such industrial cameras, with their high power consumption, would require a separate power input. But USB-C eliminates the need for an external power source for these cameras. Given the power requirements, fast data transfer rates and small form factor, USB-C presents size and heat challenges for power system designers. In addition, USB 2.0 and 3.0 have found their way into common AC outlets. Implementing USB-C into these outlets is just a natural evolution. However, packing 100W or just 15W into the little space of an AC outlet represents similar challenges and, thus, requires a small power solution with low heat dissipation.
Drones, robots and more
Large drones have tall stacks of Li-ion batteries ranging from 6 to 14 cells (21.6V to 50.4V nominal) to supply its peak power demand up to 200W. At the same time, they are still compact electronic devices where space is a premium. The same power and space demands exist for gadgets such as rechargeable robots, including those that clean floors (Figure 3); GPS trackers; and financial transaction devices like currency counters, cash registers and card readers. For efficient and reliable operation, all of these devices need to have minimal heat dissipation and low electromagnetic interference (EMI).
Designing compact power supplies
The applications discussed here share a common characteristic: a great deal of intelligence that, in turn, requires more electronics. More circuitry brings greater demand for power and higher integration, whilst increasing design complexity. Thermal management becomes more challenging, too, given the space constraints.
While Moore’s Law correctly predicted integrated digital circuitry density doubling about every two years (in other words, the same digital circuitry can reduce its size in half every two years), the same cannot be said of analogue ICs, particularly power management components. Reducing the size of such power management components has been much harder than with digital circuits. The parameter tradeoffs that need to be made are quite complex, and each of the variables to consider in an analogue design are more interdependent than they are in the digital design world.
Traditional power supplies typically come with high temperature rise and a large solution size, which makes it difficult for system designers to meet the demands for greater intelligence in their compact designs. However, advancements in power supply design have overcome these challenges. A power module architecture that taps into the latest semiconductor process and packaging technology has resulted in small solution sizes with minimal temperature rise. The architecture is the Maxim Integrated Himalaya uSLIC, based around a DC-DC technology. The Himalaya micro-sized system-level IC (uSLIC) architecture integrates with an inductor a synchronous wide-input Himalaya buck converter (with built-in FETs), compensation and other functions. The modules have wide input voltage ranges, from 2.9V to 5.5V and from 4.0V to 60V, with output current capability from 100mA to 2A. The power modules comply with the JESD22-B103/B104/B111 mechanical standard as well as the CISPR 22 EMI standard. These modules are up to 2.25x smaller than discrete solutions.
As equipment, systems, and devices in a number of application areas continue to increase in intelligence while shrinking in size, the miniaturisation of their underlying electronic components has become critical. The power supply is one area in particular that traditionally has consumed a significant portion of the PCB. However, a new power module architecture that integrates a synchronous buck converter with an inductor in tiny packages meets the thermal, size and power demands of today’s feature-rich designs.