Using supercapacitor-based energy storage, the circuit maintains power to 3.3 V systems during power interruptions and battery replacement.
EDLCBU-3V3
A reference design by Vishay gives power backup to 3.3V systems using electric double layer capacitors (EDLCs). The design is aimed at applications where there is a need to ensure continuous operations in case of power failure or replacement of the battery. The system uses supercapacitors to store the energy when operating normally and provide backup power supply in case of input voltage reduction.
This design employs a reversible buck-boost regulator to control charging and discharging processes in the EDLCs. While operating normally, it charges the supercapacitors with an average current of 2.5A while handling peak inductor currents of up to 5A. In case of input voltage reduction below 3.08V, the regulator enters into backup mode and supplies 3V of the system using energy stored in the EDLCs.
Reference design enables micro-UPS operation in 3.3V applications and comes with low quiescent current in the ready state along with an efficiency level of up to 94%. Development kit includes access to the communication pins of the regulator, which can be mounted on a breadboard for testing purposes and also helps connect more EDLCs in order to increase the backup energy capacity.
Applications of the design include hand-held instruments, portable instruments with detachable batteries, industrial sensor and actuator modules, aftermarket automotive tracking system, energy storage for IoT devices, and graceful shut-down of embedded systems.
During normal operation, energy is transferred from the system rail to the EDLCs to be stored. When the supply voltage decreases below the operating level, the regulator will automatically move the energy that is stored back to the system rail until all the energy stored in the supercapacitors is depleted. The duration of the backup depends on the total capacitance of the EDLCs used and the load used in the application, whereas the charging period depends on the peak current in the inductors.
The design uses one or more EDLC supercapacitors as the energy storage unit, making it possible to extend the backup duration by increasing the storage capacitance. This allows engineers to modify the design for different application requirements without changing the basic operating principle.
Vishay has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
