Input overcurrent suppression circuit

A DC power supply system comprising plural DC power supplies, plural DC-DC converters and plural loads, each DC power supply being connected to at least two associated DC-DC converters, of the plural DC-DC converters, for supplying respective input power currents thereto and each load being connected to at least an associated DC-DC converter, of the plural DC-DC converters, each DC-DC converter comprising:

• an input circuit connected in series circuit relationship between the DC-DC converter and the associated DC power supply supplying an input power current thereto and conducting therethrough the input power current supplied by the associated DC power supply, the input circuit comprising a parallel connection of a fusible resistor and a switch, the switch normally being in an ON condition and shunting the false resistor;
• a power-on detector detecting the initiation of supply of an input power current thereto from the associated DC power supply and producing a corresponding power-on detection output;
• a delay circuit receiving the power on detection output and, in response thereto and for a selected time thereafter, producing a first control output, the switch being turned OFF in response to the power-on detection output and the input power current being conducted by the fusible resistor of the input circuit and the fusible resistor suppressing any surge current level of the input power current for the selected time;
• and
• an over-current detector detecting an over-current level of the input power current and, in response thereto, producing an over-current detection output which is supplied to the switch and turns the switch OFF, causing the input power current of the over-current level to be conducted by and rupture the fusible resistor and thereby preventing any continuing flow of the input power supply current of the over-current level into the DC-DC converter.