DC-DC CONVERTER

摘要

The switched mode power supply according to the invention has an input voltage under-voltage indicator (12), an output voltage monitoring block (16), a circuit (23) performing a logical function and a controlled switch (24). The circuit performing a logical function functions in such a way that it controls the controlled switch (24) to close at once when the first output voltage monitoriing circuit has found that this voltage has reached its nominal value and input voltage information indicates that there is a sufficient voltage in the switched mode power supply primary. The load supplied by the switched mode power supply will hereby first be provided in a controlled manner with a first voltage (V1) and only thereafter with a second voltage (V2). If the input voltage is cutt off or it becomes too low, the circuit performing a logical function will control the switch (24) to open at once, whereby the first voltage (V1) is switched off the load. On the other hand, energy charged in capacitors of the switched mode power supply secondary circuit will keep the second voltage (V2) at its nominal value for some time. In this way, the first voltage (V1) is first switched off the load in a controlled manner and the second voltage falling according to a time constant will remain effective for some time.