1. Field of the Invention
The present invention relates to a circuit arrangement for charging rectifiers for DC energy storage devices, particularly storage batteries, in telecommunications systems, particularly telephone exchange systems, in a monitoring apparatus serving for a function check of a converter supplied by the AC voltage supply network which is offered DC voltage feed, both by an auxiliary converter and likewise from the AC voltage supply network, as well as by a DC converter supplied by a DC energy storage device, being offered thereto via a crystal diode assigned to the auxiliary converter and to the DC converter and serving the purpose of decoupling.
2. Description of the Prior Art
Monitoring equipment that serve various control functions are provided in charging rectifiers of the type set forth above and that is presumed known in the art. The monitoring of the output voltage and of the output current of the charging rectifier can be included among these control functions. Further, operating values (voltage, current and the like) determined by such a monitoring equipment can be made visible with the assistance of a display device. In addition, such a monitoring equipment can also serve for controlling the charging events. Assume a charging rectifier is controlled during normal operations such that it merely guarantees the preservation of the charge of the DC energy storage device (operating condition of "maintaining charge"). After an outage of the AC voltage supply of the charging rectifier, by contrast, care must be exercised to see that the DC energy storage device that was partially discharged during the outage is again recharged (operating condition of "charging"). To this end, the monitoring equipment measures the duration of the outage of the AC voltage supply and, if this duration has exceeded a defined, prescribed length, causes a switching of the charging rectifier to a charging condition for a defined time interval, i.e. accomplishes the recharging of the DC energy storage device.
A monitoring equipment in a circuit arrangement of the type generally set forth above can also have still further functions such as, for example, the regulation of the output voltage and/or of the output current of the charging rectifier, dependent on defined measurable variables. There is the general requirement for such monitoring equipment that they must be capable of continuing to operate given an outage of the AC voltage supply via the AC voltage supply network, for example, for the above measurement of the duration of an outage of the AC voltage supply. The DC converter is provided for this purpose, the DC voltage supply for this monitoring equipment being assured via the DC converter in case of an outage of the AC voltage supply. At the same time, however, there is the requirement that a monitoring equipment also continues to work, in particular, without interruption, when the clamp voltage of the DC energy storage device drops to such an extent, for example as a consequence of a short or of an overload, that a lower voltage limiting value below which the supply voltage for the monitoring equipment should not drop is downwardly transgressed. It is therefore provided in a circuit arrangement of the type generally set forth above that the monitoring equipment is supplied with DC voltage from two sides via two crystal diodes serving the purpose of mutual decoupling, in particular from the auxiliary converter supplied from the AC voltage supply network, on the one hand, and from the DC converter supplied by the DC energy storage device, on the other hand. When one of these two DC voltage sources fails, then the DC voltage supply of the monitoring equipment is still guaranteed to be free of interruption via the respective other of the two energy sources.
The above-described supply of the monitoring equipment with DC voltages from the DC converter, on the one hand, and from the auxiliary converter, on the other hand, however, harbors the risk that a malfunction occurring in the DC converter will not be recognized, but this makes the monitoring equipment currentless, i.e. interrupts its continued operation, when the DC voltage supply is interrupted due to a malfunction.