Requirements for Small High Efficiency DC/DC Converters in Complex Communication Networks

In complex communication networks like ISDN (Integrated Service Oigital Network) it is necessary to power the different 1/0 terminals (Input/Output) from the local mains. If the local mains fail the basic function to telephone has to be guaranteed. In such an emergency case one defined terminal of the line is powered by the exchange. To avoid reaction, caused by equalizing current, it is necessary to separate every power line of the peripheral submodules from the other and the exchange. This separation is done by small DC/DC power supplies with potentialfree outputs. These DC/DC converters are implemented on the information processing boards. At the example of the DC/DC converters for the ISDN digital TE´s (Telephone Extension) the following topics will be explained - Earthing concept of ISDN - Requirements for a DC/DC converter to power ISDN TE´s - Realization of the TE power supply with discret components - Requirements for an integrated regulator from the view of power supply manufacturer.