Supercapacitor auto-balancing MOSFET arrays operate with near-zero leakage



Advanced Linear Devices, a design innovation leader in analog semiconductors, announced a family of Supercapacitor Auto Balancing (SAB) MOSFETs to provide automatic active leakage current regulation and self-balancing of supercaps connected in a series stack. For circuit design in automotive batteries, industrial engines, mobile or energy harvesting applications, ALD’s SAB MOSFET arrays eliminate both overcharging and excessive power dissipation to preserve lifespan of supercap and battery components.

Available in both quad and dual packages, the ALD8100xx/ALD9100xx SAB MOSFETs, made with ALD’s precision EPAD technology, offer a superior alternative to other auto-balancing schemes based on passive resistors or operational amplifiers, which contribute continuous power dissipation due to linear currents at all voltage levels. Additionally, the SAB MOSFETS lower cost and power consumption and reduce board space.

Leakage differences in series-connected supercaps make it difficult to control respective voltages. This causes one or more supercap to exceed its rated voltage over time, which reduces lifespan through rupturing and leads to catastrophic failure.

The ALD8100xx/ALD9100xx SAB MOSFET family offers different threshold voltages for various supercap nominal voltage values and desired leakage balancing characteristics. By increasing drain current exponentially when voltages increase, and by decreasing drain current exponentially when voltages decrease, the MOSFET arrays regulate the voltage across a supercap cell.

“Each supercapacitor cell has a definitive maximum set voltage. However, when two or more are connected in series, it becomes difficult to control the leakage of each cell, resulting in voltage imbalance that causes one or more cell to rapidly degrade,” said Bob Chao, President of ALD. “Steady degradation of one or more of the supercaps will cause them to reach a failure point. The intrinsic qualities of SAB MOSFETS, are ideally suited to balance the supercaps and prevent the damage of excessive voltages.”

ALD SAB MOSFETs have novel electrical characteristics for active continuous leakage current regulation and self-balancing of stacked series-connected supercaps. Additionally, they are designed to dissipate near zero leakage currents, eliminating extra power dissipation.

Pricing and Availability: 
The ALD8100xx/ALD9100xx SAB MOSFET family is available in industry standard 16-Pin/8-Pin SOIC packages. 1,000-piece pricing starts at $1.12 each.

Advanced Linear Devices