Uninterruptible power supplies with converter operation conditioned upon static switch commutation and methods of operation thereof

Abstract

A UPS is operated by deasserting a static switch drive signal, e.g., a gate signal to a thyristor, and then delaying provision of power from a converter circuit of the UPS, e.g., an inverter or other source of AC power, until after the switch has current commutated to an off state. For example, expiration of a predetermined time interval following deassertion of the switch drive signal may be detected, and the converter circuit may be enabled to drive the output of the UPS responsive to the detected expiration of the predetermined time interval. Alternatively, a current in the static switch may be detected, and the converter circuit may be enabled to drive the output of the UPS responsive to the detected current. The invention may be embodied as methods and apparatus.

1 . An uninterruptible power supply (UPS), comprising:
 an AC input configured to be coupled to an AC source;   an AC output;   a converter circuit operative to generate an AC voltage at the AC output;   a switch operative to couple the AC input to the AC output through the switch responsive to a first state of a switch drive signal and to decouple the AC input from the AC output responsive to second state of the switch drive signal; and   a control circuit operative to detect a current in the switch following a transition of the switch drive signal to the second state and to initiate control of the AC output by the converter circuit following the transition of the switch drive signal to the second state responsive to the detected current.   
     
     
         2 . The UPS of  claim 1 , wherein the switch comprises a thryristor. 
     
     
         3 . The UPS of  claim 1 , wherein the control circuit is configured to initiate control of the AC output by the converter circuit responsive to the detected current meeting a predetermined criterion. 
     
     
         4 . The UPS of  claim 1 , wherein the control circuit is configured to delay provision of power by the converter circuit to the AC output responsive to the detected current. 
     
     
         5 . The UPS of  claim 1 , wherein the control circuit is configured to maintain an output of the converter circuit in a high-impedance state preceding initiation of control of the AC output by the converter circuit. 
     
     
         6 . A method of operating a UPS comprising an AC input configured to be coupled to an AC source, an AC output and, converter circuit operative to generate an AC voltage at the AC output and a switch operative to couple the AC input to the AC output through the switch responsive to a first state of a switch drive signal and to decouple the AC input from the AC output responsive to second state of the switch drive signal, the method comprising:
 detecting a current in the switch following a transition of the switch drive signal to the second state; and   initiating control of the AC output by the converter circuit following the transition of the switch drive signal to the second state responsive to the detected current.   
     
     
         7 . The method of  claim 6 , wherein the switch comprises a thryristor. 
     
     
         8 . The method of  claim 6 , wherein initiating control of the AC output by the converter circuit following the transition of the switch drive signal to the second state responsive to the detected current comprises initiating control of the AC output by the converter circuit responsive to the detected current meeting a predetermined criterion. 
     
     
         9 . The method of  claim 6 , wherein initiating control of the AC output by the converter circuit following the transition of the switch drive signal to the second state responsive to the detected current is preceded by inhibiting provision of power by the converter circuit to the AC output responsive to the detected current. 
     
     
         10 . The method of  claim 6 , wherein initiating control of the AC output by the converter circuit following the transition of the switch drive signal to the second state responsive to the detected current is preceded by maintaining an output of the converter circuit in a high-impedance state.