Smart meters are pretty cool. You can track your usage of water, gas, or electricity by the day or even the hour. And if your water, gas, or electric service is disrupted, the smart meter is kind enough to automatically report this outage to the utility company for you. Welcome to the 21st century!
Smart meters reduce costs for utility companies. Instead of sending out a “meter reader” every month to record your usage, this number is automatically reported. Smart meters also allow billing based on “estimated usages.” Finally, eliminating the need for utility personnel also reduces noisy altercations in the neighborhood by avoiding disturbing “Spike” in his backyard.
One technical issue with smart meters, or any meter, is power management. While all meters have a relatively easy connection to the grid (especially for an electricity meter), it is critical to have a backup power source. After all, it’s difficult to report an interruption in electricity service without electricity to operate. Also, usage monitoring and safety should be continuously provided, and this requires power.
A low cost, easily obtainable, and small coin cell battery is an easy choice for a backup power source. But with the reduced visits by meter readers, this coin cell battery should last a while—or else the meter readers would become “battery changers.” The electronics need 3.3V to operate in case of a power interruption, but a coin cell battery only gives between 2V and 3V. A boost converter is a viable solution, but this power converter draws some operating current, which reduces the battery life by consuming power. How do we solve this dilemma?
An ultra-low power boost + bypass converter is the answer. When the meter is operating normally and the battery is not needed, the boost converter enters a bypass mode and consumes 15 nA (yes, that’s 15 nana-Amps or 0.015 micro-Amps). In this mode, the electronics remain powered. When a power failure occurs, a micro-controller turns on the boost converter to power the electronics effectively. Since the meter operates normally with power for most of its life, the coin cell battery can last 10 years or more. Now, the meter readers turned battery changers need to find a new career: perhaps dog training.
How does an ultra-low power boost + bypass converter help your designs?