Advanced Power Conversion Technologies Detailed at Darnell Power Forum
Digitally-controlled photovoltaic power converters, advanced energy harvesting technologies and developments in power supply in package/power supply on chip (PSiP/ PwrSoC) devices were all reviewed on Tuesday at Darnell’s Power Forum. Presenters included Dave Freeman from Texas Instruments, Lonnie Johnson from Johnson Research and Development, Harry Ostaffe from Powercast and Arnold Alderman from Anagenesis Inc..
Freeman presented multiple opportunities for applying digital power technologies in photovoltaic inverters including, inverters, distributed dc-dc converters, battery management and (wireless and powerline) communications/control. He reviewed seven different maximum power point tracking (MPPT) algorithms and the applicability of digital power.
The opportunity for digital power is expected to grow even larger as distributed dc-dc converters and microinverters incorporating distributed MPPT are used in next-generation photovoltaic installations. Reviewing topologies for distributed microinverters, Freeman found that the best combination of efficiency, cost and reliability is obtained with a two-stage, non-isolated design.
Following the discussion of photovoltaic generation, Johnson presented a novel and high-efficiency ambient heat engine capable of producing an open circuit output voltage of 1.98V and trickle charging a Li-ion battery. In addition, he showed a development concept for a "perpetual micro power card." The device is the size of a credit card and is capable of harvesting RF energy, vibration energy, photovoltaic energy, ambient heat energy, acoustic energy and includes a thin-film battery for energy storage.
Continuing the focus on energy harvesting, Ostaffe presented a paper co-authored by Jason Tollefson with Microchip Technology, on implementing a low-power wireless sensor node with zero sleep power. The system employs directed RF energy as a power source. As a result, the power is reliable and deterministic, available on demand and requires no batteries for storage. Further advances are expected to result from the incorporation of high-performance antennas and improved sensitivity of the receiver circuit.
Closing the morning session, Alderman presented a review of the current state-of-the-art for PSiP and PwrSoC devices. At this time, PSiP devices offer cost and performance advantages compared with PwrSoCs. That advantage may continue for a significant time into the future if PSiPs employ more advanced interconnects, a combination of chip-on-board and flip-chip assemblies and R/L/C integration into the circuit board. Lack of efficient and cost-effective thin-film inductors is a major (and continuing) roadblock to wider-spread development of competitive PwrSoC solutions.