Multiple Output Isolated DC/DC Power Converters

Abstract

Methods of regulating an output voltage of a multi-output isolated power converter are disclosed. One method includes allowing the output voltage to vary unregulated when the output voltage is below a threshold value and preventing the output voltage from increasing when the output voltage reaches the threshold value. Additional methods and multi-output power supplies are also disclosed.

1 - 25 . (canceled) 
     
     
         26 . A multi-output power supply comprising:
 a regulated power converter for converting an input voltage to an intermediate voltage;   an isolated power converter for converting the intermediate voltage to a plurality of output voltages, the isolated power converter having an unregulated primary side switching circuit and a plurality of secondary side rectification circuits, the unregulated primary side switching circuit coupled to the intermediate voltage and a primary winding of a transformer, each of the plurality of secondary side rectification circuits coupled to one of a plurality of secondary windings of the transformer and providing one of the plurality of output voltages.   
     
     
         27 . The power supply of  claim 26  wherein the plurality of secondary side rectification circuits are unregulated. 
     
     
         28 . The power supply of  claim 27  wherein each of the plurality of secondary side rectification circuits includes at least one passive rectifier. 
     
     
         29 . The power supply of  claim 26  configured such that at least two of the plurality of output voltages are different voltages when the power supply is operating. 
     
     
         30 . The power supply of  claim 26  wherein each of the plurality of secondary side rectification circuits includes at least one synchronous rectifier. 
     
     
         31 . The power supply of  claim 30  wherein each of the plurality of output voltages is unregulated when the power supply is operating and such output voltage is below an associated threshold voltage. 
     
     
         32 . The power supply of  claim 31  wherein each of the plurality of output voltages is regulated by delaying the turn-on time of the associated synchronous rectifier when the power supply is operating and such output voltage reaches the associated threshold voltage. 
     
     
         33 - 39 . (canceled) 
     
     
         40 . A multi-output isolated power converter comprising:
 an unregulated primary switching circuit including a switch for switching an input voltage across at least one transformer primary winding;   a plurality of secondary output circuits each coupled to a transformer secondary winding, each of the plurality of secondary output circuits including a synchronous rectifier and configured to provide an output voltage when the power converter is operating;   a control circuit coupled to the switch and the synchronous rectifier of each of the plurality of secondary output circuits, the control circuit configured to provide, when the power converter is operating, a switching control signal to the switch and a rectifier control signal to the synchronous rectifier of each of the plurality of secondary output circuits; and   a regulation circuit coupled between the control circuit and the synchronous rectifier of one of the plurality of secondary output circuits, the regulation circuit operable to prevent the synchronous rectifier to which it is coupled from receiving a portion of the rectifier control signal when the output voltage of the one of the plurality of secondary output circuits exceeds a threshold.   
     
     
         41 . A method of limiting an output voltage of a multi-output isolated power converter including a transformer including a primary winding and a secondary winding, a switch coupled to the primary winding and a synchronous rectifier coupled to the secondary winding, the method comprising:
 switching the switch with a switch control signal having a substantially constant switch frequency and a substantially constant switch duty cycle to switch an input voltage across the primary winding of the transformer;   switching the synchronous rectifier with a control signal having a substantially constant rectifier frequency and a substantially constant rectifier duty cycle;   preventing the synchronous rectifier from receiving a portion of the control signal to shorten an on-time of the synchronous rectifier without otherwise altering the rectifier frequency, rectifier duty cycle, switch frequency and switch duty cycle.   
     
     
         42 . The method of  claim 41  wherein preventing the synchronous rectifier from receiving a portion of the control signal includes directing a portion of the control signal to a ground. 
     
     
         43 . The method of  claim 41  wherein the portion of the control signal the synchronous rectifier is prevented from receiving is a leading edge of the control signal. 
     
     
         44 - 47 . (canceled)