Method and apparatus for protecting a load against an overcurrent

Abstract

A hybrid load protection apparatus () comprises a primary power supply path (A) between input terminal and output terminals () and a controllable mechanical switch (A) connected in series with a primary coil (A-) coupled inductively to a secondary coil (A-) providing a voltage, U, corresponding to a current rise speed of the electrical current flowing through the primary path (A). The voltage, U, is applied directly to a driver input (IN) of a first driver circuit (A) to trigger automatically a switch-off of the mechanical switch (A) within a first switch-off period (Δt) to interrupt the primary power supply path (A). A secondary power supply path (B) is provided in parallel to the primary path (A) and having a further coil (B) connected in series with a semiconductor power switch (B). wherein a second driver circuit (B) associated with the secondary path (B) detects an increasing electrical current, I, flowing through the secondary path (B) caused by the interruption of the primary current path (A) on the basis of a voltage drop (ΔU) generated by the further coil (B) and a non-linear voltage drop (ΔU) along the semiconductor power switch (B) applied as a sum voltage (U) directly to a driver input (DESAT) at a high voltage side of the second analog driver circuit (B) to trigger automatically a switch-off of the semiconductor power switch (B) within a second switch-off period (Δt) to interrupt the secondary power supply path (B).