Abstract: To control the current through a winding interconnected in an H-bridge to control e.g. a stepping motor, at the beginning of each chopper period, the H-bridge is kept in its slow demagnetization state during predetermined interval (t1-t2). Then, just before, at or just after the end of that interval, the actual current value (IA) is compared with a desired value (ID). If the actual value (IA) is smaller, the H-bridge is kept in its magnetization state, at the most until the end of the chopper period. If the actual value is larger, the H-bridge is kept in its fast demagnetization state, at the most until the end of the chopper period. Hereby, the current is regulated to the desired value with a minimum of current ripple. This reduces the electromagnetic radiation. Also, the impact of current spikes, appearing when the H-bridge is switched, is brought to a minimum.

Abstract: A firing unit for initiation of detonators, which contain at least one base charge in a detonator casing, which firing unit comprisesan electrically actuable fuse head,a current source connected to the electrically actuable fuse head via switching means, and an electronics unit comprisinga signal decoder designed so as to distinguish a start signal supplied to the detonator via an external signal conductor,a delay circuit designed in such a way that, when the start signal is received, it supplies an ignition signal after a predetermined time andthe switching means, which are designed in such a way that, when the ignition signal is received, they connect the current source to the fuse head in order to electrically actuate the latter,the electronics unit comprising at least one chip made from a semiconductor material and having a microcircuit. According to the invention, at least the chip and an additional component are electrically and mechanically connected on a substrate having a circuit pattern.