Power converter with a variable reference voltage and inrush current limiting

A power converter, comprising:

• an active converter that includes a semiconductor element, is supplied with an AC voltage from an AC power source, rectifies the AC voltage into a DC voltage, and raises the DC voltage to an arbitrary DC voltage;
• a smoothing capacitor that is connected to an output side of the active converter with a DC load connected to both ends of the smoothing capacitor, and smoothes the DC voltage output from the active converter;
• a current limiting resistor that is connected between the AC power source and the active converter, and limits a current flowing from the AC power source;
• a switching unit that is connected in parallel with the current limiting resistor;
• a DC voltage detecting unit detecting a bus voltage that is a voltage across the smoothing capacitor;
• and
• a control device that controls a voltage-raising operation of the DC voltage output from the active converter,
• wherein the control device turns on the switching unit in a case where the AC voltage is output from the AC power source, and turns off the switching unit in a case where a power failure occurs in the AC power source,
• the control device stops an operation of the DC load when it is determined that the bus voltage detected by the DC voltage detecting unit is equal to or less than a predetermined reference voltage,
• wherein in a case where the active converter does not perform the voltage-raising operation but performs a rectification operation of the AC voltage, the control device estimates the AC voltage of the AC power source based on the bus voltage detected by the DC voltage detecting unit, subtracts a margin in consideration of a false detection due to a variation in an output voltage of the active converter, and sets the reference voltage based on a value of the estimated AC voltage.

A power converter, comprising:

• an active converter that includes a semiconductor element, is supplied with an AC voltage from an AC power source, rectifies the AC voltage into a DC voltage, and raises the DC voltage to an arbitrary DC voltage;
• a smoothing capacitor that is connected to an output side of the active converter with a DC load connected to both ends of the smoothing capacitor, and smoothes the DC voltage output from the active converter;
• a current limiting resistor that is connected between the AC power source and the active converter, and limits a current flowing from the AC power source;
• a switching unit that is connected in parallel with the current limiting resistor;
• a DC voltage detecting unit detecting a bus voltage that is a voltage across the smoothing capacitor;
• and
• a control device that controls a voltage-raising operation of the DC voltage output from the active converter,
• wherein the control device turns on the switching unit in a case where the AC voltage is output from the AC power source, and turns off the switching unit in a case where a power failure occurs in the AC power source,
• the control device stops an operation of the DC load when it is determined that the bus voltage detected by the DC voltage detecting unit is equal to or less than a predetermined reference voltage,
• wherein in a case where the active converter stops the voltage-raising operation and transits to a rectification operation, the control device lowers a voltage-raising level in a stepwise manner, and in each state of being lowered in the stepwise manner, when it is determined that a control value of the voltage-raising level with respect to the active converter is less than the bus voltage detected by the DC voltage detecting unit, the control device estimates the AC voltage of the AC power source based on the bus voltage and sets the reference voltage based on the estimated AC voltage value.