"Cap-Drop" Approach Implements Offline Power Supply for Light Loads (.PDF Download)

    Sept. 12, 2016
    Low-power applications such as e-meters (electricity or energy meters) often require a simple ac line-powered supply where a 3.3-V rail powers a microcontroller and charges a lithium-ion battery to 4.2 V. You can implement this with a mains-frequency power transformer or with a more complicated ac-dc (offline) power supply. Both approaches have well-known disadvantages related to a combination of weight, size, and complexity. Two simpler options are a full-wave capacitor-drop circuit with the bridge rectifier (Fig. 1) and similar half-wave circuit...  

    Low-power applications such as e-meters (electricity or energy meters) often require a simple ac line-powered supply where a 3.3-V rail powers a microcontroller and charges a lithium-ion battery to 4.2 V. You can implement this with a mains-frequency power transformer or with a more complicated ac-dc (offline) power supply. Both approaches have well-known disadvantages related to a combination of weight, size, and complexity. Two simpler options are a full-wave capacitor-drop circuit with the bridge rectifier (Fig. 1) and similar half-wave circuit...

    Register or Sign in below to download the full article in .PDF format, including high-resolution graphics and schematics when applicable.

    Download

    Continue Reading

    Sponsored

    The flyback topology is a versatile, widely used, switched-mode power-supply design with some interesting characteristics that brings performance and BOM advantages to many applications...
    Stricter guidelines imposed by version 3 of the IEC standard for harmonic current emissions push designers to embrace power-factor-correction methodologies.
    With the growing importance of power consumption in today's devices, dc-dc converters primarily strive for efficiency, with new technologies playing a role to achieve that goal...
    Designing power supplies that work from wall outlets has multiple challenges. This FAQ should answer many of your questions.