Many battery-operated systems use two or more supercapacitors in series. In an earlier interview, Robert L. Chao, founder, Advanced Linear Devices Inc., explained how MOSFET based current balancing is enabling reduced power use in superconductor stacks. He says, “A MOSFET array balances leakage currents in each cell by exponentially varying currents relative to selected operating voltages. This method compensates for leakage-current imbalances with small voltage imbalances so that maximum rated voltage limits are not exceeded.”
Varying models for different end applications
While designing power-conversion components, lifestyle of consumers and application of the system also define scalability of the design. Current-handling capability and failure protection of the designed circuit reflects its complexity, cost and size.
Consider the case of a metering device. Presently, a majority of digital residential meters are non-communicative, with no electronic controlling capabilities. Power requirement for such systems will hardly be 0.5W to 2W. However, futuristic smartmeters look to integrate communication capabilities and remote control facilities within, and this would demand a difference in the design. Thus, system developers design variant models of power-sourcing circuits.
Small sizes and higher packing densities automatically come with the drawback of higher heat generation. µModule from Linear Technology facilitates sharing of the heat-sink between digital microcontroller circuits and the module.
There is also another trend that is seen. Instead of adding heat-sinks and fans, the industry is trying to use the printed circuit board (PCB) itself to dissipate the heat generated. There are two developments to counter this problem. One is to use a material on the PCB that removes heat, and/or use multi-layer boards, and the other is to adopt multi-purpose packaging technologies.
Packaging plays a vital role. Requirement for reduced package size has resulted in tiny lead-less or ball grid array (BGA) packaging with extremely small pitches. This requires reduced power consumption, leading to reduced voltages. Increases in thermal stresses on chips create a requirement for thermal pads, for effective heat dissipation. Heat from the chip goes into the power pad, from where it is transferred to the surface of the PCB and then dissipated.
Quad Flat No Leads packaging is dominant. TO-XX packaging offers a wide range of small-pin-count packages for discrete parts like transistors or diodes. Smaller the package, higher is the professionalism required to solder the components.
This packaging trend not only satisfies the need to fit in maximum things into minimum space but also takes care of miniscule-size restrictions demanded by peripheral component interconnect express (PCIe) cards and wearable devices.
Making performance count
Optimising the performance of a chip within its limits of cooling, packaging and power supply capabilities is a mighty challenge. While dynamic voltage frequency scaling is one traditional method, MIC95410 7A load switch from Micrel permits power partitioning in systems, and is also capable of controlling power-up sequence using a ramp signal.
A stable and noise-free source. It is also necessary to make sure that operation of a power-sourcing circuit is stable and noise-free. In a sensor based data-acquisition circuit, a slight change in output of the powering circuit can result in large variations in sensor calibration, resulting in erroneous data. Thus, precise voltage regulation of power-sourcing circuits is of prime importance for maintaining system integrity.
Improving efficiency. Vicor has come up with Factorised Power Architecture (FPA) to solve power-related performance issues. Enabling components are integrated power components called VI Chips. FPA aims at providing the highest degree of system flexibility, power density, conversion efficiency, transient responsiveness, noise performance and field reliability.
Design with caution. Design of the PCB also comes into prominence when inductive components like motors and solenoids are involved. These components tend to create spikes in current, and PCB parts have to be designed with optimum protection to handle this surge. There is also a need to build isolation into these solutions, separating the secondary from the effects of the primary winding of the transformer.
While trends in power-conversion components are not advancing as rapidly as, say, the Internet of Things or infotainment, tried-and-tested new developments are here to stay. Keep on the lookout for more.
Priya Ravindran is a technical journalist at EFY