Inductive-load drive circuit esp. for fuel injector - reduces voltage applied to load from Zener diode string and supply transistor after rapid current redn.

摘要

The induction coil (L) is wired in series with a DMOS controlled power switch (2) and measuring resistance (3), and in parallel with two alternately connectable bipolar transistor branches (20,26). A logic circuit (14) controls the switching so that load current rises to a peak value and then falls rapidly to a holding value, about which it oscillates. A p-n-p transistor (17) reduces the voltage on the load (L). ADVANTAGE - Most reliable and inexpensive construction maintains control current always above holding current, to prevent unwanted valve closure and to exclude any period of uncontrollability.