Power converter with demand pulse isolation

Abstract

The present invention provides a switched-mode power converter with regulation demand pulses sent across a galvanic isolation barrier.

What is claimed is: 
     
       1. Apparatus configured to provide switched-mode power conversion, the apparatus comprising:
 an input port configured to receive input power;   a switch configured to commutate the input power;   galvanic isolation circuitry configured to provide galvanic isolation between the input port and an output port, wherein the galvanic isolation circuitry comprises a transformer comprising (i) a primary winding arranged in circuit with the input port and the switch and (ii) a secondary winding arranged in circuit with a rectifier and the output port, wherein the transformer is configured to transfer power from the input port to supply voltage or current to a load connected to the output port; and   a demand pulse generator galvanically connected to the secondary winding and configured to generate demand pulses applied via the galvanic isolation circuitry to the switch to adjust a frequency of the commutation of the input power to supply a desired amount of voltage or current to the load.   
     
     
       2. The apparatus of  claim 1 , further comprising:
 a source configured to provide a reference signal; and   comparison circuitry configured to compare the output port voltage or current to the reference signal wherein frequency of the demand pulses is responsive to the comparison between the output port voltage or current and the reference signal.   
     
     
       3. The apparatus of  claim 1 , further comprising input-side blocking oscillator circuitry configured to drive the switch. 
     
     
       4. The apparatus of  claim 3 , wherein the demand pulse generator comprises output-side blocking oscillator circuitry configured to generate the demand pulses. 
     
     
       5. The apparatus of  claim 1 , further comprising:
 a fast oscillator configured to initiate the generation of the demand pulses; and   logic circuitry configured to provide gating of the demand pulses applied to the galvanic isolation circuitry.   
     
     
       6. The apparatus of  claim 1 , wherein the galvanic isolation circuitry further comprises dedicated circuitry configured to convey the demand pulses across the galvanic isolation. 
     
     
       7. The apparatus of  claim 1 , wherein the demand pulses are conveyed from the demand pulse generator to the switch via the transformer. 
     
     
       8. The apparatus of  claim 1 , wherein:
 the galvanic isolation circuitry divides the apparatus into (i) an input side corresponding to the primary winding of the transformer and (ii) an output side corresponding to the secondary winding of the transformer; and   the demand pulse generator is located on the output side of the apparatus.   
     
     
       9. The apparatus of  claim 1 , further comprising a capacitor and a diode both galvanically connected to the secondary winding, wherein:
 the diode is different from the rectifier and is poled to charge the capacitor during forward pulses of the apparatus; and   the demand pulse generator is powered by energy stored in the capacitor to generate the demand pulses.   
     
     
       10. Apparatus configured to provide galvanically isolated switched-mode power conversion, the apparatus comprising:
 an input port configured to receive input power;   a switch configured to commutate the input power;   a transformer comprising (i) a primary winding arranged in circuit with the input port and the switch and (ii) a secondary winding arranged in circuit with a rectifier and an output port, wherein the transformer is configured to supply power from the input port to a load connected to the output port; and   a first pulse source circuitry located on an input side of the apparatus and configured to generate pulses to control the switch to start the power conversion; and   a second pulse source circuitry located on an output side of the apparatus and configured to generate pulses to control the switch to continue the power conversion after being started by the first pulse source circuitry.   
     
     
       11. The apparatus of  claim 10 , wherein the frequency of pulses generated by the second pulse source circuitry is different from the frequency of pulses generated by the first pulse source circuitry. 
     
     
       12. The apparatus of  claim 11 , wherein the frequency of pulses generated by the second pulse source circuitry is greater than the frequency of pulses generated by the first pulse source circuitry. 
     
     
       13. The apparatus of  claim 10 , wherein the frequency of pulses generated by the first pulse source circuitry is about 1 KHz or smaller. 
     
     
       14. The apparatus of  claim 13 , wherein the frequency of pulses generated by the second pulse source circuitry is about 60 KHz or greater. 
     
     
       15. The apparatus of  claim 10 , further comprising a capacitor and a diode both galvanically connected to the secondary winding, wherein:
 the diode is different from the rectifier and is poled to charge the capacitor during forward pulses of the apparatus; and   the second pulse source circuitry is powered by energy stored in the capacitor to generate the pulses.   
     
     
       16. In an isolated switched-mode power converter having an input port and an output port, a method of regulation comprising:
 (a) comparing a voltage or current at the output port with a reference that is galvanically associated therewith;   (b) generating or gating demand pulses responsive to that comparison;   (c) applying the demand pulses to an output-port side of galvanic isolation circuitry;   (d) receiving replicas of the demand pulses from an input-port side of the galvanic isolation circuitry; and   (e) adjusting commutation frequency of the converter responsive to the demand pulses to cause the voltage or current at the output port to attain a desired value.    
     
     
       17. The method of  claim 16 , wherein step (b) comprises:
 (b1) using a diode to charge a capacitor during forward pulses of the power converter, wherein the diode and the capacitor are galvanically connected within the output-port side of the galvanic isolation circuitry; and   (b2) generating or gating the demand pulses using energy stored in the capacitor.   
     
     
       18. Circuitry for controlling a flyback converter, the flyback converter comprising:
 a converter primary side comprising an input port;   a converter secondary side comprising an output port, wherein the converter secondary side is galvanically isolated from the converter primary side; and   a power transformer configured to transfer input power received at the input port to provide output power at the output port, wherein:
 the converter primary side further comprises a primary-side switch configured to selectively transfer the input power at the input port via the power transformer to the output power at the output port; 
 the circuitry comprises primary-side circuitry and secondary-side circuitry, wherein, when the circuitry is configured to control the flyback converter, (i) the primary-side circuitry is on the converter primary side and (ii) the secondary-side circuitry is on the converter secondary side; 
 the secondary-side circuitry (i) determines when to turn on the primary-side switch based on output port voltage or current at the output port and (ii) generates corresponding demand pulses; 
 the converter secondary side is configured to transmit the demand pulses to the converter primary side; 
 the primary-side circuitry is configured to turn on the primary-side switch in response to the demand pulses conveyed from the converter secondary side to the converter primary side, wherein the primary-side circuitry, and not the secondary-side circuitry, originates the determination of when to turn off the primary-side switch; 
 frequency with which the primary-side switch is turned on is adjusted by the demand pulses conveyed from the converter secondary side to the converter primary side to regulate the output port voltage or current; and 
 the converter secondary side further comprises:
 a first capacitor; and 
 a first rectifier poled to charge the first capacitor during forward power converter pulses of the flyback converter, wherein the demand pulses are generated using energy stored in the first capacitor. 
 
   
     
     
       19. The circuitry of claim 18, wherein the converter secondary side further comprises a second capacitor, different from the first capacitor, and a second rectifier, different from the first rectifier, wherein flyback voltage of the power transformer is rectified by the second rectifier and charges the second capacitor to supply the output port voltage or current. 
     
     
       20. The circuitry of claim 18, wherein
 the first rectifier is part of the secondary-side circuitry.   
     
     
       21. The circuitry of claim 18, wherein the flyback converter is configured to charge the first capacitor during flyback power converter pulses of the flyback converter. 
     
     
       22. The circuitry of claim 18, wherein the flyback converter is configured to charge the first capacitor during forward power converter pulses of the flyback converter even if the output port is short-circuited. 
     
     
       23. The circuitry of claim 18, wherein:
 the secondary-side circuitry is configured to generate a demand pulse when a feedback signal based on the output port voltage or current is lower in magnitude than a magnitude of a reference signal such that the demand pulses regulate the output port by driving the feedback signal to match the reference signal;   the flyback converter regulates the output port to have the feedback signal match the reference signal;   frequency of the demand pulses generated by the secondary-side circuitry is greater than frequency of pulses initiated on the converter primary side that turn on the primary-side switch;   the secondary-side circuitry generates a demand pulse whenever a magnitude of the output port voltage or current is below a magnitude of the output port's regulation voltage or current;   the primary-side switch is turned on for a duration that is independent of duration of the demand pulse that caused the primary-side switch to be turned on;   the secondary-side circuitry is configured to adjust the frequency of turning on the primary-side switch to supply a desired amount of voltage or current to the output port in order to regulate the output port; and   the converter secondary side comprises:
 a reference source configured to provide a reference signal; and 
 a secondary-side comparator configured to compare a feedback signal based on the output port voltage or current to the reference signal wherein the frequency of the demand pulses is responsive to a comparison between the feedback signal and the reference signal. 
   
     
     
       24. The circuitry of claim 23, wherein:
 the primary-side circuitry comprises the primary-side switch;   the converter secondary side further comprises a second capacitor, different from the first capacitor, and a second rectifier, different from the first rectifier, wherein flyback voltage of the power transformer is rectified by the second rectifier and charges the second capacitor to supply the output port voltage or current;   the converter secondary side is configured to charge the first capacitor during flyback power converter pulses of the flyback converter;   the converter secondary side is configured to charge the first capacitor during forward power converter pulses of the flyback converter even if the output port is short-circuited;   the first rectifier is part of the secondary-side circuitry;   feedback from the converter secondary side to the converter primary side for regulating the output port voltage or current is provided solely by the demand pulses generated by the secondary-side circuitry;   the secondary-side comparator generates a comparator output;   the secondary-side circuitry comprises:
 an oscillator configured to generate a stream of oscillator pulses independent of the comparator output; and 
 logic circuitry configured to (i) receive the comparator output and the stream of oscillator pulses and (ii) process, based on the comparator output, the stream of oscillator pulses to generate the demand pulses by selectively blocking certain oscillator pulses; 
   regulation of the output port is based solely on the demand pulses generated on the converter secondary side;   the flyback converter is configured such that the power transformer transfers unipolar input power received at the input port to provide the output power at the output port;   the converter primary side further comprises a primary-side magnetically coupled conductor;   the converter secondary side further comprises a secondary-side magnetically coupled conductor configured to be magnetically coupled to the primary-side magnetically coupled conductor to convey the demand pulses from the converter secondary side to the converter primary side;   the power transformer has a primary-side winding and a secondary-side winding;   the primary-side switch is connected in series with the primary-side winding of the power transformer;   the secondary-side winding of the power transformer is connected to the output port;   the primary-side magnetically coupled conductor is different from the primary-side winding of the power transformer;   the secondary-side magnetically coupled conductor is different from the secondary-side winding of the power transformer;   the primary-side circuitry comprises a primary-side oscillator configured to generate one or more primary-side pulses;   the primary-side switch is configured to be turned on based on (i) the one or more primary-side pulses generated by the primary-side oscillator and (ii) the demand pulses received from the converter secondary side;   the primary-side circuitry is configured to turn on the primary-side switch at power up, in order to transfer input power to the converter secondary side via the power transformer to power the secondary-side circuitry to generate the demand pulses; and   the converter secondary side does not generate pulses instructing the converter primary side to turn off the primary-side switch.   
     
     
       25. The circuitry of claim 18, wherein the secondary-side circuitry is configured to generate a demand pulse when a feedback signal based on the output port voltage or current is lower in magnitude than a magnitude of a reference signal such that the demand pulses regulate the output port by driving the feedback signal to match the reference signal. 
     
     
       26. The circuitry of claim 25, wherein the flyback converter regulates the output port to have the feedback signal match the reference signal. 
     
     
       27. The circuitry of claim 18, wherein feedback from the converter secondary side to the converter primary side for regulating the output port voltage or current is provided solely by the demand pulses generated by the secondary-side circuitry. 
     
     
       28. The circuitry of claim 18, wherein:
 each demand pulse conveyed from the converter secondary side to the converter primary side has a leading edge; and   when a particular demand pulse results in a particular occurrence of the primary-side switch turning on, the particular occurrence of the primary-side switch turning on is in response to detecting the leading edge of the particular demand pulse independent of any other demand pulses conveyed from the converter secondary side to the converter primary side and independent of any other pulse edges appearing on the converter primary side.   
     
     
       29. The circuitry of claim 18, wherein the secondary-side circuitry comprises:
 an oscillator that generates oscillator pulses, each oscillator pulse representing logic 1; and   logic circuitry that selectively blocks certain oscillator pulses in generating the demand pulses.   
     
     
       30. The circuitry of claim 29, wherein the logic circuitry is not an OR gate. 
     
     
       31. The circuitry of claim 29, wherein the logic circuitry selectively blocks certain oscillator pulses from becoming demand pulses that would otherwise result in the primary-side switch being turned on, while selectively allowing other oscillator pulses to become the demand pulses that do result in the primary-side switch being turned on. 
     
     
       32. The circuitry of claim 18, wherein frequency of the demand pulses generated by the secondary-side circuitry is greater than frequency of pulses initiated on the converter primary side that turn on the primary-side switch. 
     
     
       33. The circuitry of claim 18, wherein the secondary-side circuitry generates a demand pulse whenever a magnitude of the output port voltage or current is below a magnitude of the output port's regulation voltage or current. 
     
     
       34. The circuitry of claim 18, wherein the secondary-side circuitry processes, based on a comparator output, a secondary-side stream of pulses to generate the demand pulses. 
     
     
       35. The circuitry of claim 18, wherein the secondary-side circuitry comprises:
 a comparator configured to generate a comparator output based on a comparison between (i) a feedback signal based on the output port voltage or current and (ii) a reference signal;   an oscillator configured to generate a stream of pulses independent of the comparator output; and   logic circuitry configured to (i) receive the comparator output and the stream of pulses and (ii) process, based on the comparator output, the stream of pulses to generate the demand pulses.   
     
     
       36. The circuitry of claim 18, wherein regulation of the output port is based solely on the demand pulses generated on the converter secondary side. 
     
     
       37. The circuitry of claim 18, wherein the determination of when to turn off the primary-side switch is always originated on the converter primary side and never on the converter secondary side. 
     
     
       38. The circuitry of claim 18, wherein the flyback converter is configured such that the power transformer transfers unipolar input power received at the input port to provide the output power at the output port. 
     
     
       39. The circuitry of claim 18, wherein, unless the primary-side switch is already on due to a pulse generated on the primary side, the primary-side switch is turned on once for each different demand pulse. 
     
     
       40. The circuitry of claim 18, wherein:
 the converter primary side further comprises a primary-side magnetically coupled conductor; and   the converter secondary side further comprises a secondary-side magnetically coupled conductor configured to be magnetically coupled to the primary-side magnetically coupled conductor to convey the demand pulses from the converter secondary side to the converter primary side.   
     
     
       41. The circuitry of claim 40, wherein:
 the power transformer has a primary-side winding and a secondary-side winding;   the primary-side switch is connected in series with the primary-side winding of the power transformer;   the secondary-side winding of the power transformer is connected to the output port;   the primary-side magnetically coupled conductor is different from the primary-side winding of the power transformer; and   the secondary-side magnetically coupled conductor is the secondary-side winding of the power transformer.   
     
     
       42. The circuitry of claim 40, wherein:
 the power transformer has a primary-side winding and a secondary-side winding;   the primary-side switch is connected in series with the primary-side winding of the power transformer;   the secondary-side winding of the power transformer is connected to the output port;   the primary-side magnetically coupled conductor is different from the primary-side winding of the power transformer; and   the secondary-side magnetically coupled conductor is different from the secondary-side winding of the power transformer.   
     
     
       43. The circuitry of claim 42, wherein:
 the primary-side circuitry comprises the primary-side magnetically coupled conductor; and   the secondary-side circuitry comprises the secondary-side magnetically coupled conductor.   
     
     
       44. The circuitry of claim 40, wherein:
 the power transformer has a primary-side winding and a secondary-side winding;   the primary-side switch is connected in series with the primary-side winding of the power transformer;   the secondary-side winding of the power transformer is connected to the output port;   the primary-side magnetically coupled conductor is the primary-side winding of the power transformer; and   the secondary-side magnetically coupled conductor is the secondary-side winding of the power transformer.   
     
     
       45. The circuitry of claim 18, wherein:
 the primary-side circuitry comprises a primary-side oscillator configured to generate one or more primary-side pulses; and   the primary-side switch is configured to be turned on based on (i) the one or more primary-side pulses generated by the primary-side oscillator and (ii) the demand pulses received from the secondary-side circuitry.   
     
     
       46. The circuitry of claim 18, wherein primary-side circuitry is configured to turn on the primary-side switch for a duration that is independent of duration of the demand pulse that caused the primary-side switch to be turned on. 
     
     
       47. The circuitry of claim 18, wherein the primary-side circuitry is configured to turn on the primary-side switch at power up, in order to transfer input power to the converter secondary side via the power transformer to power the secondary-side circuitry to generate the demand pulses. 
     
     
       48. The circuitry of claim 18, wherein the primary-side circuitry does not receive pulses from the converter secondary side instructing the primary-side circuitry to turn off the primary-side switch. 
     
     
       49. The circuitry of claim 18, wherein the primary-side circuitry is configured to avoid premature turnoff of the primary-side switch due to capacitive charging of the primary-side switch. 
     
     
       50. The circuitry of claim 18, wherein the primary-side circuitry is configured to establish a maximum duration for which the primary-side switch is allowed to stay on. 
     
     
       51. The circuitry of claim 18, wherein the primary-side circuitry is configured to receive power from a bias winding of the converter primary side. 
     
     
       52. The circuitry of claim 18, wherein the primary-side circuitry is configured to determine when to turn off the primary-side switch based on either (i) current flowing through the primary-side switch or (ii) a maximum duration for which the primary-side switch is allowed to stay on. 
     
     
       53. The circuitry of claim 18, wherein the secondary-side circuitry is configured to adjust the frequency of turning on the primary-side switch to supply a desired amount of voltage or current to the output port in order to regulate the output port. 
     
     
       54. The circuitry of claim 18, wherein the secondary-side circuitry comprises:
 a reference source configured to provide a reference signal; and   a secondary-side comparator configured to compare a feedback signal based on the output port voltage or current to the reference signal wherein frequency of the demand pulses is responsive to the comparison between the feedback signal and the reference signal.   
     
     
       55. The circuitry of claim 24, wherein:
 each demand pulse conveyed from the converter secondary side to the converter primary side has a leading edge; and   when a particular demand pulse results in a particular occurrence of the primary-side switch turning on, the particular occurrence of the primary-side switch turning on is in response to detecting the leading edge of the particular demand pulse independent of any other demand pulses conveyed from the converter secondary side to the converter primary side and independent of any other pulse edges appearing on the converter primary side.   
     
     
       56. The circuitry of claim 24, wherein the determination of when to turn off the primary-side switch is always originated on the converter primary side and never on the converter secondary side. 
     
     
       57. The circuitry of claim 24, wherein, unless the primary-side switch is already on due to a pulse generated on the converter primary side, the primary-side switch is turned on once for each different demand pulse. 
     
     
       58. The circuitry of claim 24, wherein the primary-side circuitry is configured to avoid premature turnoff of the primary-side switch due to capacitive charging of the primary-side switch. 
     
     
       59. The circuitry of claim 24, wherein the primary-side circuitry is configured to establish a maximum duration for which the primary-side switch is allowed to stay on. 
     
     
       60. The circuitry of claim 24, wherein the primary-side circuitry is configured to receive power from a bias winding of the converter primary side. 
     
     
       61. The circuitry of claim 24, wherein the primary-side circuitry is configured to determine when to turn off the primary-side switch based on either (i) current flowing through the primary-side switch or (ii) a maximum duration for which the primary-side switch is allowed to stay on. 
     
     
       62. The circuitry of claim 18, wherein the demand pulses are transmitted from the secondary-side circuitry to the primary-side circuitry via inductive galvanic isolation circuitry. 
     
     
       63. The circuitry of claim 18, wherein the demand pulses are transmitted from the secondary-side circuitry to the primary-side circuitry via capacitive galvanic isolation circuitry. 
     
     
       64. The circuitry of claim 18, wherein the demand pulses are transmitted from the secondary-side circuitry to the primary-side circuitry via optocoupled galvanic isolation circuitry. 
     
     
       65. The circuitry of claim 18, wherein the demand pulses are transmitted from the secondary-side circuitry to the primary-side circuitry via piezoelectric galvanic isolation circuitry.