Voltage stabilizer

#This invention relates to a circuit arrangement for providing a stabilized output direct voltage from an unstabilized input direct voltage provided at two output terminals of a direct current source, by making use of a series control element with a control path, conveniently formed by the collector/emitter path of a transistor, and an energy storage arrangement including inductance connected directly with the series control element, the series control element being connected with one output terminal and the energy storage arrangement with the other output terminal of the direct voltage source, the end of the inductance connected with the series control element being connected with the said other output terminal of the direct voltage source by way of a diode poled so that it is forward biased by turn-off voltages appearing across the said inductance, and the series control element being arranged to be periodically controlled by a drive circuit responsive to the difference between a reference voltage and the voltage appearing at the end of the inductance opposite to that which is connected with the series control element and with the diode.

#A circuit arrangement of the kind set out above is already known from the German published Patent Specification As 1 049 962. In this known circuit arrangement the energy storage arrangement is formed by the series combination of an inductor and a capacitor, across which the output direct voltage may be derived. The drive circuit is then formed by a multivibrator circuit including two transistors. In this multivibrator there is applied to the bases of the two transistors as a control signal a voltage derived from the voltage on the capacitor, that is proportional to the difference between the instantaneous actual voltage and a reference voltage representing the desired output voltage. In this manner the duration of one half-wave of the output voltage of the multivibrator is appropriately altered. By way of a transformer connected to the collectors of the two transistors there is controlled an auxiliary transistor, which is coupled in a bistable trigger circuit with the series control element formed by a transistor. Apart from the fact that this known circuit arrangement is thus burdened with the disadvantage of a relatively high production cost, the use of this circuit arrangement may lead to difficulties, more particularly owing to damage to the semiconductor components resulting from the flow of very high currents, when a plurality of these circuit arrangements are used in parallel or when a short circuit appears in the output circuit supplied by such a circuit arrangement.

#The object of the invention is to construct a circuit arrangement of the kind initially described in such a manner that its output circuit is protected against short circuits and so that if required a plurality of such circuit arrangements may be connected in parallel in a simple manner.

#FIG. 1 shows the circuit diagram of an embodiment of circuit arrangement in accordance with the invention including a parallel push-pull inverter;

#FIG. 2 shows another embodiment of the invention including a bridge inverter; FIG. 3 shows a circuit arrangement in accordance with the invention in which the power loss in a smoothing circuit is reduced; and

#FIG. 4 shows an advantageous modification of the circuit arrangement described in relation to FIG. 3.

#The circuit arrangement represented in FIG. 1 includes a direct voltage source G1 such as a rectifier circuit, providing an unstabilized input voltage between its two output terminals e1 and e2. To terminals e1, e2 is connected a series combination consisting of the collector/emitter path of a transistor T1 employed as a series control element, an inductor L and a parallel push-pull inverter forming an inverter circuit Ts and including two transistors T2 and T3, the collector/emitter paths of which are connected mutually in parallel by way of respective windings W1 and W2 of a push-pull transformer Ue1, which also possesses further windings W3, W4. All the transistors T1, T2, T3 are here of the same conductivity type, in fact of the npn type. To the bases of the transistors T2 and T3 in the inverter circuit Ts there is connected a control circuit St, indicated only schematically in FIG. 1; this control circuit St normally includes two mutually connected additional windings of the push-pull transformer Ue1. The free ends of the mutually connected windings are connected with the bases of the respective transistors T2, T3, and their mutually connected ends are connected, possibly by way of a resistor, to the output terminal e2 of the direct voltage source G1.

#The cathode of a diode D1 is connected to the junction of the emitter of the transistor T1 with the inductance L formed by a choke coil. The anode of the diode D1 is connected with the output terminal e2 of the direct voltage source G1.

#The anode of a diode D2 is connected with the junction of the choke coil L with the two windings W1, W2 of the push-pull transformer Ue1. The cathode of the diode D2 is likewise connected with the output terminal e2 of the direct voltage source G1 by way of a parallel RC combination including a resistor R and a capacitor C1.