Hot-pluggable power component with pre-charging circuit

摘要

An improved pre-charge circuit is described for pre-charging the output capacitors in hot-pluggable power components including switch-mode rectifiers. When the hot-pluggable component is inserted into a power plant a pre-charge pin connects the output capacitor (Co) across the system bus (22, 24) through a current limiting resistor (Rcp) which determines the maximum pre-charging current through the output capacitor. Due to the resistance of the current limiting resistor and a pre-load and secondary bias circuit (30) connected across the output of the power component, the output capacitor is unable to charge to close enough of the system voltage to prevent a significant disturbance on the system bus when the power component is fully inserted. To allow the output capacitor to charge to a voltage closer to the system voltage, a resistance (Rpc) is placed in parallel with the current limiting resistor by means of a switch (Qpc). The switch is turned on when the output is significantly charged, i.e. 70% to 90% of the system voltage. This resistance in parallel with the current limiting resistor reduces the effective resistance seen by the system bus through the pre-charge pin and allows the output capacitor to be charged to very near the system voltage. <IMAGE>