Join us for Part 3 of 4 in the Richardson RFPD “A Walk Around the Block” webinar series. This series focuses on energy storage systems – leveraging the components to enable higher performance and lower system costs.
Super capacitors or Double Layer Capacitors have rapidly become a recognized and acceptable solution for storing energy in a wide variety of applications. These devices are a compromise between traditional “dielectric” capacitors and batteries. Supercapacitors not only provide a high capacitance per unit volume possibly more importantly they provide the ability to charge and discharge at exceptionally high rates of speed. Thus supercapacitors very high levels of current charge & discharge translate into an ability to deliver high specific power levels. This feature is one of supercapacitors most sought after features – massive specific power capability.
This feature also creates a problem for designers since typical power supplies cannot supply the very large currents that an uncharged supercapacitor will draw.
Enter the concept of charge control.
Charge control can be achieved through either passive or active methods and are determined through a combination of cost, space and power limitations on a design by design basis.
Fixed value resistors are examples of passive solutions and exhibit the expected advantages of small size, easy to implement and low cost. However these methods are always dissipating energy and are not necessarily suitable for electronics that will be used in wide temperature range applications or exhibit a large number of thermal excursions. Further, these devices can get physically large when dealing with high amounts of current and under those conditions they generate potentially significant amounts of heat.
The use of P channel MOSFETs or charge control ICs provides high levels of charge control in small to medium areas but with increased costs. It should be noted that costs are dropping as volumes increase and further the time needed to implement these solutions is also greatly diminishing. Many standard IC chipsets used in conjunction with supercapacitors generally offer features grouped into one or more of the following
- Cell Balance Control
- Current Control
- Balance Control & Overvoltage Protection
- Back-Up & Voltage Regulation
Charge control design has never been easier to implement given the expanded choices for designers.
- See the basic characteristics of supercapacitors
- Learn the advantages and disadvantages of passive and active charge control
- Understand basic de-rating advice to enhance supercapacitor reliability