The blinking clock syndrome: improving customer perceptions of residential power quality using double-layer capacitors

Digital clocks are found in many household appliances such as alarm clocks, microwave ovens, and VCRs. Many of these clocks contain insufficient capacitor ride-through capability or ineffective battery backup. Therefore, these devices are very sensitive to short duration power interruptions. These interruptions manifest themselves by causing the clock display to blink, which in turn causes the customer's perception of the power quality of the utility to be negative. Described in this paper is a UPS which employs double-layer capacitors for the backup power supply. The UPS design is based on a push-pull amplifier that utilizes a simple oscillator circuit to produce the 60 Hz AC voltage needed for the load. The UPS has been constructed and extensively tested in the laboratory on a digital alarm clock. Backup power can provided to the clock for over 30 seconds using a double-layer capacitor bank, which is sufficient since most power interruptions are cleared within 30 seconds.