Inrush current control for AC to DC converters

• US 6,493,245 B1
• Filed: 08/15/2001
• Issued: 12/10/2002
• Est. Priority Date: 08/15/2001
• Status: Expired due to Fees

• Current Assignee: Astec International Limited (Emerson Electric Company)
• Original Assignee: Astec International Limited (Emerson Electric Company)
• Inventors: Phadke, Vijay Gangadhar
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/930,818
• Time in Patent Office: 482 Days
• Field of Search: 323/908, 363/53, 363/54, 363/84, 363/88
• US Class Current: 363/54
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• CPC Class Codes: H02M 1/0085 Partially controlled bridges
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

The present invention provides for an apparatus and corresponding method for controlling inrush current in an AC-DC power converter by controlling the state of a plurality of silicon-controlled rectifiers (SCRs) when AC power is lost. The present invention provides full control of inrush current even during cold startup, warm startup, and power line disturbance conditions. The present invention controls inrush current without the need for an extra series dissapative device and its consequent additional losses. The preferred embodiment includes use of the present invention for AC-DC converters having active power factor correction. An alternative embodiment is for use in non-power factor corrected applications.

Claims

1. A method of controlling inrush current in a AC-DC converter when AC power is lost during power line disturbance conditions comprising the steps of:

a) Maintaining a plurality of SCRs in an OFF state to limit inrush current when said AC power is lost;

b) Comparing the instantaneous AC input voltage to the DC output voltage of the converter;

c) Comparing the instantaneous AC input voltage to a predetermined voltage level; and

d) Triggering said plurality of SCRs to the ON state only when said AC power is restored to said predetermined level and the instantaneous input AC voltage is less than the DC voltage at the output of the AC-DC converter.

2. A circuit for providing control of inrush current in an AC to DC power converter during power disturbance conditions, wherein the AC to DC converter includes two input terminals to which AC power is coupled and two output terminals where the output DC power is provided, comprising:

a bridge rectifying circuit including a plurality of SCRs;

a circuit to provide a drive bias for said plurality of SCRs;

an output capacitor connected across said output terminals of the converter;

a control circuit for controlling the rectifying circuit to limit inrush current, the control circuit being operatively connected to the gate inputs of said plurality of SCRs; and

means for comparing the AC input and DC output voltages of the converter for causing said plurality of SCRs to enter a conduction state when said AC input voltage exceeds a predetermined threshold and said AC input voltage is less than the DC output voltage.