Abstract: An improved signal converter which isolates a measurement voltage by converting an analog signal into a pulse-width-modulated output signal. The converter has a first integrator followed in series by a threshold value controller whose output signal actuates at least one reversing switch element which supplies to the summing point of the first integrator at which the signal prevails, and to the threshold value controller, either a positive or negative reference voltage. This signal converter has a very low offset and a high linearity at high sampling rates. The signal also has a second integrator whose summing point is also connected to the signal input and output of the reversing switch element. The output signal of the second integrator is the reference signal of the first integrator. The linearity of the signal converter is thus exclusively dependent upon the parameters of the second integrator.

Abstract: A protective circuit for a switching transistor is disclosed in which the base-emitter voltage of the switching transistor is compared in a comparator with a reference voltage. If the collector current of the switching transistor increases, the base-emitter voltage also increases, with the base current remaining constant. As soon as the base-emitter voltage exceeds the reference voltage, a signal is delivered at the output of the comparator. A switching-off device for switching off the driving pulses of the switching transistor responds to this signal so that a switching-on pulse present at the base of the switching transistor is switched off. The reference voltage is fixed so that the switching transistor is protected against overload by excessively large collector currents.

Abstract: A triangle waveform generator having a comparator which drives an integrator via a limiter is disclosed. At the output of the integrator, the desired triangular waveform voltage is present. The output of the integrator is connected to a first input of the comparator. The output of the comparator is fed back to its first input via a resistor. The output of the integrator is coupled via an integral action controller to a second input of the comparator. The integral action controller has a substantially longer time constant than the integrator. With this circuit, a triangular voltage is obtained, the parameters of which, namely, the slope and the positive and negative peak values, depend only on resistors and reference voltages which can be set within narrow tolerances.

Abstract: Method and circuitry for generating drive pulses for a DC control element of the type having four semiconductor switches arranged in a bridge circuit. Two triangular voltage waveforms are formed and are shifted with respect to one another by a difference voltage. Each bridge branch of the bridge circuit is driven in response to a comparison between the first triangular voltage waveform and a control voltage, and a second semiconductor switch of each bridge branch is driven in response to a comparison of the second triangular voltage waveform and the same control voltage. A pause between the conductive periods of the semiconductor switches within a bridge branch is obtained by driving the semiconductor switches with offset triangular voltage waveforms. The pauses prevent short circuits of a supply voltage source, and their duration is determined by the difference voltage and can therefore be achieved accurately at low cost.

Abstract: A signalling apparatus has at least one transmitter in a transmitter assembly for transmitting a signal by impressed current to several spatially separated receivers. A series circuit of threshold members is connected to the output terminals of each transmitter, the number of members corresponding to the number of receivers. The input of each receiver is connected to a threshold member; the receivers are therefore connected in series on the input side. It is ensured thereby that the same current flows through all receivers. In the event of a failure of a transmission line or a receiver, the current continues to flow through the associated threshold member so that signal transmission to the other receivers continues uninterrupted.

Abstract: A short-circuit protection device for a DC control element has at least one transistor which is addressed by timing pulses obtained by comparison of a triangular voltage with a control voltage. Each such transistor is provided with a separate overcurrent protection device which, after a short circuit, blocks the associated transistor until the beginning of a new switching-on pulse. The control voltage assumes values which are above the maximum value of the triangular voltage.In the event of a short circuit, the transistor concerned is switched off very fast, but is switched on again by the next succeeding switching-on pulse and a determination is made as to whether the short circuit is still present.

Abstract: An overload protection circuit for a semiconductor switch has a control line which can be shorted, via the collector-emitter path of a transistor, to the ground. The base of the transistor is connected to the output of a comparison stage. One input of the comparison stage is connected via a resistor to the control line, via a diode to the lead of the semiconductor switch facing away from the ground potential, and via a capacitor to ground. A fixed reference voltage is applied to the second input of the comparator stage.In this circuit, a control pulse is shorted as soon as the voltage across the semiconductor switch exceeds a given value because of overcurrent. The short circuit of the addressing pulse is cancelled again as soon as the latter goes back to zero.

Abstract: A method and apparatus for driving a transistor wherein a control voltage and a cut-off voltage are applied to the base of the transistor to cause the transistor to conduct current and to cut-off, respectively, and wherein, preceding the application of the cut-off voltage, a further voltage is applied to the base of the transistor for a predetermined desaturation time interval .DELTA.t which depends upon the storage or delay time of the transistor. In accord with the invention, the aforesaid further voltage corresponds to the voltage at which the current at the base of the transistor is approximately zero.