Drive circuit for printer, particularly, matrix printer of the needle or hammer variety

摘要

The drive circuit for an electromagnetic actuator for the impact element in a printer includes a series circuit of a drive transistor and of a switching transistor there being a reference resistor interposed which together with a Zener diode serves as a current limiter for the current through the drive transistor and the electromagnetic element. The two transistors are controlled in that each of the base electrodes is serially connected to the emitter collector path of a control transistor and the two control transistors in turn are connected to monostable multivibrators which are triggered concurrently but furnish pulses of different duration such that the switching transistor is turned off before the drive transistor. The current limiting permits utilization of residual electromagnetic energy from the preceding actuation pulse without incurring undue losses.