Freescale Semiconductor is demonstrating what it describes as a breakthrough in power conversion technology for photovoltaic (PV) applications this week at the Applied Power Electronics Conference and Exposition (APEC).
Freescale claims that it has developed advanced, ultra-low-voltage dc-dc converter technology that enables industry-leading solar cell startup and operating performance and efficiency at levels as low as 0.32V, as well as operation down to 0.25V.
According to the company, most ICs cannot start up at voltages less than the typical turn-on voltage of a transistor (approximately 0.7V) without external assistance. This limitation is said to reduce system design options and increases the complexity of power conversion and energy recovery applications involving ultra-low voltages.
Freescale’s power conversion technology enables IC startup thresholds to be reduced to 0.32V and efficiencies of nearly 90%. The company claims that this technology can enable practical and cost-effective ways to develop a wide range of single-cell solar power systems and other energy-harvesting applications, such as thermoelectric and mechanical scavenging systems. Potential applications include solar-powered battery chargers, trickle chargers for automotive systems, chargers for cell phones and laptops, remote data acquisition and industrial HVAC systems, PV-based traffic signals, solar-powered home and commercial lighting products, and self-powered wireless transponders.
The Freescale demo showcases a small, portable solar charging system for a lithium ion (Li-Ion) battery. VIN and VOUT meters show the conversion between input and output voltage (directly boosting 0.32 to 4V) enabled by Freescale’s dc-dc converter IC.
Using a low-cost single solar cell, Freescale’s power conversion technology is engineered to charge a Li-Ion battery cell at 100mA. Present charging systems require multiple solar cells in series, which drives up cost, reduces efficiency and increases sensitivity to shading and cell mismatches.
"We see nothing currently available in the semiconductor industry approaching the ultra-low-voltage capability and power conversion efficiency of our analog technology demonstrated at APEC," said Arman Naghavi, Vice President and General Manager of Freescale’s Analog, Mixed-Signal and Power Division. "Freescale has demonstrated a solution that addresses one of the most difficult technological and practical challenges of extracting power from a single solar cell. This breakthrough can be used to help reduce the cost and streamline the development of innovative solar chargers, energy-harvesting systems and other low-voltage energy sources."
According to the company, the exceptional performance and efficiency of the dc-dc power conversion technology is achieved through a combination of SMAR™OS 10 process technology, optimized flip-chip on leadframe (FCOL) packaging and IC design. Freescale’s 130-nanometer SMAR™OS 10 technology is engineered to enable both low voltage operation and high efficiency.
Samples of Freescale’s dc-dc power converter ICs and evaluation boards are available for qualified customers.