Sperrdiode

A Sperrdiode, or blocking diode, is an electronic device designed to prevent current from flowing in the reverse direction while allowing current to pass in the forward direction. It is a two-terminal component that conducts when forward biased and presents a high impedance when reverse biased, effectively blocking reverse currents in many circuit configurations.

Operation and ratings: In forward bias, a silicon diode typically exhibits a forward voltage drop of about 0.6 to 0.7 volts at moderate currents, with the drop increasing slightly as current rises. In reverse bias, only a small leakage current flows until the diode reaches its breakdown voltage, at which point destructive current can occur. The practical use of a Sperrdiode depends on its maximum reverse voltage (VR) and continuous forward current (IF), along with its leakage characteristics, thermal behavior, and, for fast-switching applications, recovery time.

Variants and considerations: The standard PN junction diode is the traditional Sperrdiode. Schottky barrier diodes offer lower forward voltage drops (often 0.15 to 0.45 V) and faster switching but typically have higher reverse leakage and lower reverse voltage ratings. In power electronics, many designs employ ideal-diode or MOSFET-based arrangements to further reduce forward losses while preserving reverse-blocking function.

Applications: Sperrdiodes are widely used for reverse polarity protection, preventing backflow in power supplies, diode-ORing for redundant supplies, and blocking discharge of energy storage devices into sources such as solar panels or batteries. They are also used to isolate circuit sections during operation or maintenance.

Limitations and selection: Choosing a Sperrdiode involves balancing forward voltage drop, reverse voltage rating, forward current capability, leakage, and thermal considerations. Higher-efficiency applications may favor Schottky or intended ideal-diode solutions to minimize voltage loss.