Control system for a power converter and method of operating the same

Abstract

A power converter employing a control system configured to make multiple functional use of a circuit node therein and method of operating the same. In one embodiment, the power converter includes a power train including at least one power switch. The power converter also includes a control system including an opto-isolator circuit, including a resistor, configured to receive an output signal from the power converter and provide a feedback signal to a feedback node for the control system to provide a switch control signal for the at least one power switch. The control system also includes a current source configured to produce multiple voltage levels at the feedback node in accordance with the resistor, thereby enabling multiple functional uses of the feedback node.

What is claimed: 
     
         1 . A control system, comprising:
 an opto-isolator circuit, including a resistor coupled between an optical isolator of said opto-isolator circuit and a feedback node of said control system, said opto-isolator circuit configured to receive an output signal from a power converter and provide a feedback signal to said feedback node to provide a switch control signal for a power switch of said power converter; and   a comparator coupled to said feedback node and configured to enable a hiccup mode of operation of said power converter when a voltage at said feedback node exceeds a threshold level.   
     
     
         2 . The control system as recited in  claim 1  further comprising another comparator coupled to said feedback node and configured to enable a latching shutdown mode of operation of said power converter when said voltage at said feedback node exceeds a further threshold level. 
     
     
         3 . The control system as recited in  claim 2  wherein said latching shutdown mode of operation is maintained by a pair of switches emulating a thyristor that shorts a bias voltage source to local circuit ground. 
     
     
         4 . The control system as recited in  claim 1  further comprising a switched current source coupled to said feedback node and configured to inject a level of current into said feedback node during a complementary duty cycle of said power converter. 
     
     
         5 . The control system as recited in  claim 4  wherein a value of said resistor is selected in conjunction with said level of current of to provide a voltage offset for said feedback node during said complementary duty cycle of said power converter. 
     
     
         6 . The control system as recited in  claim 4  wherein said level of current produces a voltage to set a time limit for short-term over-current protection for said power converter. 
     
     
         7 . The control system as recited in  claim 1  further comprising another resistor coupled between said optical isolator and local circuit ground, a resistance of said another resistor selected to adjust a level of voltage of said feedback node. 
     
     
         8 . The control system as recited in  claim 1  further comprising a current mirror coupled to said feedback node to produce a current in a timing capacitor to control a duty cycle of said power converter. 
     
     
         9 . The control system as recited in  claim 1  further comprising at least one diode coupled to said feedback node to limit an operational characteristic of said control system. 
     
     
         10 . A method, comprising:
 to receiving an output signal from a power converter;   providing a feedback signal to a feedback node to provide a switch control signal for a power switch of said power converter; and   enabling a hiccup mode of operation of said power converter when a voltage at said feedback node exceeds a threshold level.   
     
     
         11 . The method as recited in  claim 10  enabling a latching shutdown mode of operation of said power converter when said voltage at said feedback node exceeds a further threshold level. 
     
     
         12 . The method as recited in  claim 11  wherein said latching shutdown mode of operation is maintained by a pair of switches emulating a thyristor that shorts a bias voltage source to local circuit ground. 
     
     
         13 . The method as recited in  claim 10  further comprising injecting a level of current into said feedback node during a complementary duty cycle of said power converter. 
     
     
         14 . A power converter, comprising:
 a power train including at least one power switch; and   a control system, including:
 an opto-isolator circuit, including a resistor coupled between an optical isolator of said opto-isolator circuit and a feedback node of said control system, said opto-isolator circuit configured to receive an output signal from said power converter and provide a feedback signal to said feedback node to provide a switch control signal for said at least one power switch of said power converter, and 
 a comparator coupled to said feedback node and configured to enable a hiccup mode of operation of said power converter when a voltage at said feedback node exceeds a threshold level. 
   
     
     
         15 . The power converter as recited in  claim 14  wherein said control system further comprises another comparator coupled to said feedback node and configured to enable a latching shutdown mode of operation of said power converter when said voltage at said feedback node exceeds a further threshold level. 
     
     
         16 . The power converter as recited in  claim 15  wherein said latching shutdown mode of operation is maintained by a pair of switches emulating a thyristor that shorts a bias voltage source to local circuit ground. 
     
     
         17 . The power converter as recited in  claim 14  wherein said control system further comprises a switched current source coupled to said feedback node and configured to inject a level of current into said feedback node during a complementary duty cycle of said power converter. 
     
     
         18 . The power converter as recited in  claim 17  wherein a value of said resistor is selected in conjunction with said level of current of to provide a voltage offset for said feedback node during said complementary duty cycle of said power converter. 
     
     
         19 . The power converter as recited in  claim 14  wherein said control system further comprises another resistor coupled between said optical isolator and local circuit ground, a resistance of said another resistor selected to adjust a level of voltage of said feedback node. 
     
     
         20 . The power converter as recited in  claim 14  wherein said control system further comprises a current mirror coupled to said feedback node to produce a current in a timing capacitor to control a duty cycle of said power converter.